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TRANSCRIPT
STAFF REPORT
RECOMMENDED REMEDIAL ACTION
For
Lakeside Reclamation Landfill Beaverton, Oregon
ESCI # 4413
Prepared By
OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY
Northwest Region Office
August 2011
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TABLE OF CONTENTS
1. INTRODUCTION .............................................................................................................................................. 1
1.1 INTRODUCTION ........................................................................................................................................... 1 1.2 SCOPE AND ROLE OF THE RECOMMENDED REMEDIAL ACTION .................................................... 1 1.3 PEER REVIEW SUMMARY ......................................................................................................................... 2
2. SITE DESCRIPTION AND HISTORY ........................................................................................................... 3
2.1 SITE LOCATION AND LAND USE .............................................................................................................. 3 2.2 BENEFICIAL WATER USES ........................................................................................................................ 4 2.3 PHYSICAL SETTING .................................................................................................................................... 5 2.4 LANDFILL OPERATIONS ............................................................................................................................ 9
3. REMEDIAL INVESTIGATION .................................................................................................................... 12
3.1 CONCEPTUAL SITE MODEL .................................................................................................................... 12 3.2 COVER EVALUATION ............................................................................................................................... 12 3.3 GROUNDWATER ........................................................................................................................................ 15 3.4 CONTAMINANT FATE AND TRANSPORT ............................................................................................. 18 3.5 SURFACE WATER ...................................................................................................................................... 18 3.6 SOIL .............................................................................................................................................................. 20 3.7 TUALATIN RIVER SEDIMENT ................................................................................................................. 21 3.8 RISK ASSESSMENT ................................................................................................................................... 22 3.9 IDENTIFICATION OF HOT SPOTS ........................................................................................................... 26
4. DESCRIPTION OF REMEDIAL ACTION ALTERNATIVES ................................................................. 27
4.1 REMEDIAL ACTION OBJECTIVES .......................................................................................................... 27 4.2 GROUNDWATER PLUME AREA AND VOLUME ................................................................................... 27 4.3 APPLICABLE REQUIREMENTS ............................................................................................................... 28 4.4 LANDFILL COVER REMEDIAL ACTION ALTERNATIVES ................................................................. 28 4.5 GROUNDWATER REMEDIAL ACTION ALTERNATIVES .................................................................... 30 4.6 PERIODIC REVIEW, MONITORING AND CONTINGENCIES ............................................................... 33
5. EVALUATION OF REMEDIAL ACTION ALTERNATIVES .................................................................. 35
5.1 EVALUATION CRITERIA .......................................................................................................................... 35 5.2 PROTECTIVENESS ..................................................................................................................................... 35 5.3 BALANCING FACTORS ............................................................................................................................. 38
6. COMPARATIVE ANALYSIS OF ALTERNATIVES ................................................................................. 45
6.1 LANDFILL COVER ..................................................................................................................................... 45 6.2 GROUNDWATER REMEDIAL ACTION ALTERNATIVES .................................................................... 47 6.3 TREATMENT, REUSE AND DISPOSAL OF EXTRACTED WATER......................................................................... 49
7. RECOMMENDED REMEDIAL ACTION ALTERNATIVES ................................................................... 52
7.1 DESCRIPTION OF RECOMMENDED LANFILL COVER ALTERNATIVE ........................................... 52 7.2 DESCRIPTION OF THE RECOMMENDED GROUNDWATER ALTERNATIVE .................................. 52 7.3 ADAPTIVE MANAGEMENT .............................................................................................................................. 54 7.4 RESIDUAL RISK ASSESSMENT ............................................................................................................... 55
8. ADMINISTRATIVE RECORD INDEX ........................................................................................................ 56
Figures
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1. Site Location Map
2. Regional Geologic Map
3. Regional Geologic Cross Section
4. Site Geologic Cross Section
5. Shallow Groundwater Flow – Water Table Surface
6. Surface Water Features and the Locality of Facility
7. Site Features and Monitoring Locations
8. Groundwater Quality -Total Dissolved Solids
9. Groundwater Quality – Iron
10. Groundwater Quality – Manganese
11. Groundwater Quality – Chloride
12. Tree Distribution on Evapo-Transpiration Cover
13. Site Cross Section – Groundwater Contamination
14. Conceptual Site Model of Potential Human Exposure
15. Conceptual Site Model of Potential Ecological Exposure
16. Groundwater Hot Spot
Tables
1. Detections in Riverside Wells – Contaminants with Ecological Screening Values
2. Detections in Riverside Wells – Contaminants without Ecological Screening Values
3. Comparison of Upgradient and Downgradient Water Quality
4. Data Summary and Chemistry-Toxicity Screening of COIs in Groundwater
5. Cumulative Ecological Risk Screening
6. Remedial Action Levels
7. Comparison of Remedial Action Alternatives
8. Comparison of Groundwater Treatment/Disposal Alternatives
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1. INTRODUCTION
1.1 INTRODUCTION
This report presents DEQ‟s recommended remedial action for the Lakeside Reclamation Landfill
site (Lakeside) at 14930 SW Vandermost Road in Beaverton, Oregon. DEQ developed the
recommended remedial action in accordance with Oregon Revised Statutes (ORS) 465.200 et. seq.
and Oregon Administrative Rules (OAR) Chapter 340, Division 122, Sections 0010 through 0115
and OAR chapter 340, Division 40, sections 0040 through 0050.
The recommended remedial action is based on the administrative record for this site. A copy of the
Administrative Record Index is attached as Appendix A. This report summarizes the more detailed
information contained in the Remedial Investigation, Baseline Risk Assessment, Ecological Risk
Assessment and Feasibility Study reports completed under Oregon Department of Environmental
Quality (DEQ) Voluntary Agreement No. LQVC-NWR-05-08 dated December 9, 2005.
1.2 SCOPE AND ROLE OF THE RECOMMENDED REMEDIAL ACTION
The recommended remedial action addresses Lakeside‟s cover, and groundwater contamination
beneath and downgradient of the landfill currently discharging to the Tualatin River. The
contaminants of concern include ammonia, barium, calcium, chloride, iron, magnesium, manganese
and zinc. DEQ identified these chemicals based on: 1) their risks to aquatic organisms of the
Tualatin River and the degradation of the river‟s aquatic environment, and 2) the frequency and
consistency with which they exceed their respective ecologically based screening levels and/or
ambient water quality criteria. The remedy also addresses sporadically detected contaminants of
ecological concern such as selenium and cyanide and conditions and contaminants associated with
general water quality degradation including high chemical oxygen demand, depleted oxygen levels,
and high total dissolved solids.
The recommended remedial action consists of the following elements:
1) Enhancements to the evapotranspiration (ET) cover to improve tree growth, density, and
long-term health and to reduce the volume of water leaching landfill waste and releasing
contaminants to the environment;
2) Hydraulic containment of the plume of groundwater contamination through installation and
pumping from approximately 12 groundwater extraction wells;
3) Treatment of wastewater using on-site and/or off-site land application and subsequent
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evapo-transpiration and contaminant uptake by trees, or beneficial re-use of the wastewater
for moisture control for Lakeside‟s composting operations;
4) Performance monitoring to: A) demonstrate hydraulic containment of the groundwater
plume has been achieved and is maintained over time, B) assess contaminant concentrations
over time, C) ensure land application/ of wastewater is not adversely impacting the soil
column and groundwater, and D) demonstrate compliance with ET cover performance
criteria (currently set at an infiltration rate of less than 1.0 inches of water annually).
5) Contingency measures administered through an Adaptive Management process that will be
implemented if the hydraulic containment system does not meet remedial objectives, if land
application causes adverse impacts, or if the ET cover does not meet performance
objectives. Refer to Section 7.3 for discussion of the adaptive management process.
1.3 PEER REVIEW SUMMARY
Plans and reports produced during the investigation of the Lakeside site have been reviewed by the
Project Manager/Hydrogeologist Henning Larsen, a solid waste and Environmental Engineer, Tim
Spencer, and Toxicologist Paul Seidel. The team unanimously supports the recommended remedial
action. Refer to the technical team evaluation file for more detailed information. Additionally, Bill
Mason, DEQ Western Region senior hydrogeologist, reviewed the staff report and concluded it is
consistent from a programmatic and regulatory basis.
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2. SITE DESCRIPTION AND HISTORY
Lakeside Reclamation Landfill is a 37-acre former construction debris landfill that closed in 2009.
The landfill is owned by Grabhorn Inc. When filling operations began in the early 1950s waste
was placed directly on native soils, thus it is an unlined landfill. In 1991, Lakeside began closing
sections of the landfill with an evapotranspiration cover consisting primarily of hybrid poplar
and pine trees. Currently, final grading of the landfill cover is nearing completion and a plan for
enhancing the cover‟s performance is under development. The only structure associated with the
landfill is a small building formerly used as a scale house by employees weighing loads of waste
entering the facility. The landfill is roughly rectangular in shape and its 1400-foot southern edge
borders the Tualatin River. The landfill is approximately 130 feet in height. The base of the landfill
ranges from an elevation 120 feet above mean sea level in the south to 170 feet in the north with a
crown elevation of approximately 250 feet above mean sea level.
2.1 SITE LOCATION AND LAND USE
The landfill is located at 14930 SW Vandermost Road in Beaverton, Oregon, Township 2S, Range
1W, Section 12, Washington County [See Figure 1]. The site latitude is 45.41 and the longitude is -
122.87.
Lakeside is located along the Tualatin River in rural Washington County, approximately 0.8 miles
west of the City of Beaverton Urban Growth Boundary and approximately 0.75 miles south of
Scholls Ferry Road. Land use within a 1 mile radius of Lakeside is a mixture of small nonfarm
residential parcels on “exception land”, urban development within the boundary, and land
designated by Washington County as “Resource Land,” zoned for Exclusive Farm Use (EFU) or
Forestry (FF). The properties occupied by the Lakeside facility and the areas proposed for land
application are designated by Washington County as “Exclusive Farm Use‟ Crops grown in the
vicinity of the landfill include Christmas trees, filberts, and grapes (vineyards). The nearest
residence is approximately 600 feet of the western facility boundary and a vineyard and associated
buildings are on the adjacent property to the east. Three wetlands listed in the National Wetlands
Inventory are located adjacent to the former landfill and three others are located within one half mile
of the facility. Within a mile of the landfill, several units of the Tualatin River Wildlife refuge are
located along the Tualatin River upstream and downstream of the landfill. Several wetlands listed
in the National Wetlands Inventory are also located within one mile.
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2.2 BENEFICIAL WATER USES
2.2.1 Groundwater
Lakeside completed a beneficial use determination for groundwater and surface water prior to the
Feasibility Study (Beneficial Water Use and Land Use Determination – Lakeside Reclamation
Landfill). This determination evaluated beneficial uses for each water-bearing zone, considering
current use and the following factors listed in OAR 340-122-080(3)(f)(F):
Historical land and water uses
Anticipated future land and water uses
Concerns of community and nearby property owners
Regional and local development patterns
Regional and local population projections
Availability of alternate water sources
The reasonable likely future beneficial uses of groundwater in the vicinity of Lakeside include:
Discharge to and sustaining of aquatic environments in the Tualatin River by the shallow
water-bearing zone occurring within alluvial and lacustrine deposits at the site.
Deep water-bearing zones occurring within interflow zones of the Columbia River Basalt
group for domestic drinking/water, supplying livestock, and irrigation, although there are no
current uses within the Locality of Facility1(LOF).
2.2.2 Surface Water
Beneficial uses of the Tualatin River include aesthetics, recreation (i.e. swimming, fishing), and
wildlife and aquatic habitat. Beneficial uses of nearby wetlands include: groundwater recharge,
and wildlife and aquatic habitat.
1Defined in OAR 340-122-115(35) (35) "Locality of the facility" means any point where a human or an ecological
receptor contacts, or is reasonably likely to come into contact with, facility-related hazardous substances,
considering: (a) The chemical and physical characteristics of the hazardous substances; (b) Physical, meteorological,
hydrogeological, and ecological characteristics that govern the tendency for hazardous substances to migrate
through environmental media or to move and accumulate through food webs; (c) Any human activities and
biological processes that govern the tendency for hazardous substances to move into and through environmental
media or to move and accumulate through food webs; and (d) The time required for contaminant migration to occur
based on the factors described in subsections (35)(34)(a) through (c) of this rule.
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2.3 PHYSICAL SETTING
Geographically, Lakeside Reclamation Landfill lies near the eastern edge of the Tualatin Basin
south of Cooper Mountain and west of Bull Mountain. The landfill‟s southern edge borders the
Tualatin River, a slowly flowing, low gradient tributary of the Willamette River. To the east the
facility site is bounded by a perennial creek (unnamed) that discharges to the Tualatin River. At the
site, the Tualatin flows east through a gap in the Chehalem Mountains. These mountains form
topographic highs located north and east of the Lakeside. The landfill sits on a terrace of recent
Tualatin River alluvial deposits, and extends from this lower river terrace roughly 2500 feet north.
The top of the landfill slopes gently to the north and blends into the land surface of the upper
terrace.
2.3.1 Climate
The climate in the valleys west of the Cascades is characterized by mild year-round
temperatures, abundant winter rains, and dry summers. The average annual temperature is
approximately 52-54F. Data provided by the Western Regional Climate Center indicates average
annual precipitation in the Beaverton area is approximately 39 inches, falling primarily in the form
of rain. The majority of the precipitation falls between October and March, with monthly totals
ranging from 4.0 to 7.0 inches. December is generally the wettest month. Precipitation totals for the
remainder of the year are generally less than 2 inches per month.
2.3.2 Geology
2.3.2.1 Regional
Lakeside Reclamation Landfill lies within the Tualatin Basin, an Eocene age pull-apart basin
formed by regional tectonic forces (i.e. where crustal plates are moving away from each other). The
basin is defined by the Coast Range Mountains to the west, the Tualatin Mountains to the north, and
the Chehalem Mountains to the south.
The deepest geologic formation relevant to the site is the Columbia River Basalt (CRB) group,
Miocene to Pliocene age theolitic flood basalts originating in western Idaho, southeastern
Washington and northeastern Oregon. Within the valley this formation is typically 500 to700 feet
thick with the upper 100-200 feet deeply weathered and decomposed. In the Tualatin Basin tectonic
forces deformed the basalt and deeper formations to create a synclinal structure (fold) that was
subsequently filled with alluvial and lacustrine deposits during the Pliocene and Pleistocene ages
(See Figures 2 and 3).
The most extensive of the valley fill sediments is the Willamette Silt, which forms the valley floor.
It ranges from 30 ft to several hundred feet thick within the Tualatin Basin. The Willamette Silt was
deposited in the Tualatin Basin after sands and gravels transported by the Bretz Floods dammed the
mouth of the Willamette River causing water to back up and flood the Tualatin Basin. Geologically,
the Willamette Silt in this area is described as unconsolidated, very fine micaceous silt and silty
sand. Entrenched within the Willamette Silt are Holocene age river channel and overbank deposits
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associated with the present day Tualatin River.
2.3.2.2 Site
The southern portion of the landfill overlies an alluvial terrace formed by the Tualatin River. This
terrace, referred to in site documents as the lower terrace, consists of sand and silty-sand river
channel deposits and sandy silt, silt, and clayey silt overbank deposits extending from the surface to
a depth of about 60 feet below ground surface. At the facility site, this terrace extends
approximately 1100 feet north to a relatively steep escarpment that rises 60 feet to an upper terrace
composed of the Willamette Silt which forms the broader valley floor.
Adjacent to the Tualatin River, terrace deposits are underlain by the very fine sediments of the
Helvetia Formation. At Lakeside, the Helvetia Formation is primarily clay and silty clay deposits
that extend to depths of at least 100 feet below ground surface. The Helvetia Formation is likely
contemporaneous with the Troutdale formation observed in the Portland Basin. In the vicinity of the
site, the Helvetia Formation appears to pinch out to the north where the Willamette Silt lies directly
over the Columbia River Basalt [See Figure 4].
2.3.3 Hydrogeology
2.3.3.1 Shallow Sedimentary Deposits
On the facility site the uppermost aquifer is present in two different hydrogeologic units. Near
the Tualatin River, the sand and silt channel and overbank terrace deposits represent the
uppermost groundwater-bearing zone. Northward on the upper terrace, the water table occurs
within the Willamette Silt. Water table depths range from 25 to 38 ft below ground surface near
the landfill‟s north end and 7 to 22 feet below ground surface near the Tualatin River. Because of
their fine-grained structure and limited thickness these shallow sediments transmit small volumes
of groundwater, thereby restricting discharge to the river. The flow direction in shallow
groundwater generally mimics surface topography. Near the site shallow groundwater flows
south and southwest, discharging to the Tualatin River [See Figure 5]. Local precipitation is the
primary source of shallow groundwater recharge.
The groundwater hydraulic gradient is approximately 0.01 ft/ft in the lower terrace deposits and
estimated seepage velocities are 25 to 50 feet per year. The shallow groundwater and the
Tualatin River are hydraulically connected, although a thick layer of fine-grain material that
forms the River channel influences the rate and locations of groundwater discharge to the river.
Consequently, changes in river stage directly influence groundwater levels and shallow
groundwater flow, but the influence is muted by the presence of the fine-grained sediments. For
most of the year the river is a gaining stream (groundwater discharges to the river), however in
the winter months during periods of high river stage the direction of flow may reverse with water
flowing away from the river recharging adjacent alluvial deposits. The area within which these
flow reversals occur is limited to about 300 feet away from the river channel.
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DEQ compared the U.S. Geological Survey‟s measured seepage rates in river channel deposits
with groundwater flow rates in the shallow aquifer estimated from Lakeside‟s monitoring well
tests. This analysis and hydrostratigraphy of the site suggest that pore water beneath the river‟s
landfill reach is dominated by groundwater that has passed beneath the landfill.
2.3.3.2 Columbia River Basalt
The site‟s most productive groundwater-bearing zones occur within Columbia River Basalt
complex. As noted in section 3.8.1, shallow groundwater within the valley fill sediments are not
hydraulically connected to the water-bearing zones within the Columbia River Basalt group,
preventing contamination from migrating into these aquifers under natural conditions.
The basalt‟s aquifer horizons generally are associated with intra-flow structures (e.g., vesicular
flow-top breccias and flow-foot breccias) of sheet flows. The interiors of thick basalt flows have
very limited permeability and act as aquitards. These structural features typically create a series
of stacked, confined aquifers within the CRB aquifer system. In these aquifers the dominant
groundwater flow usually follows horizontal to sub-horizontal pathways along individual,
laterally extensive, interflow zones. Vertical groundwater movement through undisturbed basalt
flow interiors is greatly restricted unless basalt flow interiors are disturbed or fractured (by folds
or faults), truncated (by flow pinchout and erosional windows), or cross-connected by wells.
Aquifers within the basalt units can be very productive. In the site vicinity individual
agricultural wells can produce from 50 to200 gallons per minute. In the Tualatin Valley‟s eastern
portion the Columbia River Basalt is recharged by precipitation falling on highland areas such as
the Tualatin and Chehalem Mountains. Near Lakeside, the groundwater flow direction in CRB
aquifers is unknown but the Willamette River is the assumed regional discharge area for these
aquifers.
2.3.4 Surface Water and Stormwater Features
The major surface water features near Lakeside are: 1) the Tualatin River which flows adjacent
to the landfill‟s southern boundary for approximately 1400 feet; 2) an unnamed creek that
roughly parallels the landfill boundary approximately 500 to1000 feet east of the former waste
disposal area; 3) a cluster of four manmade irrigation ponds located along the landfill‟s southeast
boundary; 4) two areas (PEM1A and PFOA, Figure 6) included in the U.S. Fish and Wildlife‟s
National Wetlands Inventory (NWI) and located within the cleanup site LOF (where
groundwater from beneath the landfill may flow into or under these areas; 5) three wetland areas
located within 1500 feet of the landfill but likely outside the site LO, and 6) A surface water seep
near the boat ramp on the Lakeside facility property, that is wet year round and at times forms
small down-stream pools before flowing into the Tualatin River. These features are presented in
Figure 6.
2.3.4.1 Tualatin River
The Tualatin River‟s main stem is roughly 80 miles long and flows generally from west to east.
The river originates in the forested Coast Range mountains and empties into the Willamette
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River near West Linn, Oregon. The river‟s characteristics change dramatically from its
headwaters to its mouth. The headwater reach, from river mile 79.4 to 55.3, is narrow, has an
average slope of 74 feet per mile, and includes several waterfalls.
Once the river reaches the valley floor, its slope decreases and it begins to meander. This
meandering reach (river miles 55.3-33.3) has an average slope of 1.3 feet per mile, a width of
about 50 feet, and relatively complete riparian shading. Downstream of the meandering reach,
the river flows into a backwater reach (river miles 33.3- 3.4) with an estimated slope of only 0.08
feet per mile. The backwater characteristics are caused both by the low slope of the basin and the
presence of a low-head dam at river mile 3.4. In this reach, the river continues to meander and
widens to roughly 150 feet. These characteristics expose much of the river surface to direct
sunlight and solar insolation. From the low-head dam to the mouth (river miles 3.4-0.0), the
Tualatin is characterized by small pools and riffles, with an average slope of 13 feet per mile.
The Tualatin River‟s discharge rises and falls as a function of seasonal rainfall amounts. Most of
the annual precipitation falls between October and March, and seasonal stream flow is typically
highest from December through April and lowest from July through October. The low-flow
summer period is defined as May 1st through October 31st. Since January of 1975, Tualatin
River stream flow has been augmented during this low-flow period with water releases from
Henry Hagg Lake, a man-made reservoir on Scoggins Creek. River flow is managed in an
attempt to maintain 150 cubic feet per second (cfs) of flow at river mile 33.3. Mean annual
stream flow in the Tualatin averaged 1,362 cubic feet per second between 1940 and 1957.
In addition to Scoggins Creek, the Tualatin River has four other major tributaries, Gales Creek,
Dairy Creek, Rock Creek and Fanno Creek. The regional sanitary authority, Clean Water
Services, operates four wastewater treatment plants in the basin, but only the two largest plants
discharge into the Tualatin River during the May 1 to October 31 period. Currently, the Rock
Creek (river mile 38.1) and Durham (river mile 9.3) wastewater treatment plants discharge a
combined flow of approximately 80 cubic feet per second (52 million gallons per day) of treated
effluent into the river or approximately 40 percent of its typical low summer flow (approximately
200 CFS). These discharges strongly influence water quality and chemistry within the Tualatin
river during low flow periods.
Lakeside is located between river miles 20 and 21, within the backwater reach. In the backwater
reach the streambed is uneven and forms occasional deep pools (15-18 ft in depth). Heavy
sedimentation occurs there due to the river‟s low gradient and channel geometry. Thick deposits
of organic material collect in depositional zones during the low-flow season. The oxygen
demand of these organic-rich sediments contributes to low dissolved oxygen conditions in the
river.
The Tualatin River is water quality limited for several chemicals and parameters including
phosphorus, dissolved oxygen, and temperature for which total maximum daily loads (TMDLs)
have been established. It is also designated as water quality limited for iron, manganese, and
arsenic, although TMDLs have not been established for these contaminants. Leachate contaminated
groundwater from the landfill potentially exacerbates these conditions due to depleted oxygen
levels, high chemical oxygen demand (COD), elevated phosphorus, iron, manganese, and arsenic.
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2.3.4.2 Unnamed Creek
As described earlier, an unnamed perennial creek flows just east of the landfill and discharges to
the Tualatin River. Lakeside diverts some creek flow to fill and maintain the on-site ponds at an
elevation of 128 feet above mean sea level. The creek receives no direct discharges from the
landfill or the ponds. Based on groundwater elevation and water quality data, is does not appear
to receive any contaminated seepage from the shallow aquifer.
2.3.4.3 Stormwater
The landfill has an immature and underperforming evapotranspiration cover that allows a
portion of the incident precipitation to infiltrate. As a consequence, the ET cover significantly
reduces stormwater runoff; however, periods of heavy precipitation can produce overland flow
on some of the steeper landfill slopes and along access roads. The landfill itself does not have a
site-wide stormwater collection or treatment system. In 2009 Lakeside installed a localized
stormwater collection system and a lined stormwater holding pond along the landfill‟s northwest
boundary. The stormwater system is designed to capture stormwater from paved site access roads
and building roofs. Lakeside does not discharge the impounded stormwater, but instead uses it
to irrigate Lakeside‟s orchards and tree farms in summer months. There is no direct discharge to
surface water, and therefore, DEQ does not require a permit.
2.4 LANDFILL OPERATIONS
The Grabhorn family started the landfill operation in the early 1950s (Note: solid waste facilities
in the State of Oregon were not required to be permitted by DEQ until 1972). In 1972, Grabhorn
Incorporated and submitted a permit application for Lakeside. Later that year DEQ issued an
operating permit to Lakeside. The 1972 permit application indicates the landfill had a footprint
of approximately 7 acres. The permit restricted the fill to materials like construction/demolition
debris and tree prunings, although, Lakeside did receive case-by-case authorizations from DEQ
to take limited amounts of non-putrescible and non-hazardous industrial wastes.
Filling initially began in the landfill‟s southern portion and progressed northward until the
facility‟s closure in 2009. Waste and debris were trucked in and deposited within the landfill
working face. Lakeside then spread and compacted the waste with heavy equipment including
waste compactors. The DEQ permit required Lakeside to cover the compacted waste with
interim soil cover at the end of each week to help contain and stabilize wastes until they placed
final cover.
In 1991, Lakeside proposed using a type of alternative evapo-transpiration final cover to close
completed portions of the landfill. DEQ analyzed the cover‟s potential performance and
compared the proposal to conventional final soil covers. DEQ approved Lakeside‟s use of the
evapo-transpiration cover. The cover, vegetated with grass, shrubs, and various tree species
including poplars and pines, now covers approximately 37 acres of the landfill. Lakeside‟s
landfill closure permit required completion of the final cover for the entire 37 acre waste disposal
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area in 2010. Lakeside has since planted the closed landfill with a mixture of deciduous and
coniferous trees.
Lakeside currently operates under a DEQ closure permit issued March 27, 2008. As specified in the
permit, the landfill stopped accepting waste on July 1, 2009. At closure, the landfill had a total
footprint of 36 acres. The landfill‟s original planned size was about 43 acres but the closure permit
required Lakeside to close early. Since its 2009 closure, Lakeside has accepted clean soils to bring
the landfill up to grade and to create a final soil profile that will support the cover system.
Lakeside started composting and recycling operation concurrent with the start of landfilling
operations. DEQ did not have a separate permit for composting until the late 1990s. In the late
1990s, Lakeside obtained a permit and operated the adjacent composting facility under a separate
DEQ solid waste facility permit. The recycling and composting operation, located northeast of the
landfill, continues to receive source-separated wastes and process yard wastes and woody debris.
Lakeside composts yard wastes, and grinds clean woody debris to produce wood chips that are used
for bio-filter bags, agricultural bedding, and other marketable products. Lakeside also continues to
accept recycled concrete and asphalt, which they use for maintaining onsite roads and for other on-
site and off-site construction projects and for sale, including stormwater control facilities.
2.4.1 Groundwater Compliance Monitoring
For many years, Lakeside‟s solid waste permit has required routine groundwater monitoring at
designated compliance points to identify leachate releases from the landfill. Quarterly groundwater
monitoring began in 1987 with two shallow wells (MW-3 and MW-4) installed downgradient of
the landfill, between its southern edge and the Tualatin River. Over time, Lakeside added additional
wells to the compliance network and by 1997 the number had increased to seven riverfront
compliance wells (MW-3, MW-4, MW-6, MW-7, MW-8, MW-9, MW-10), and one background
well (UG-1) to characterize up-gradient water quality (See Figure 7). While UG-1 is screened
within the Willamette Silt and weathered basalt hydrogeologic formations downgradient
compliance wells are completed into recent alluvial sediments, Although the two hydrogeologic
units have different properties and origins for most chemical parameters of interest the upgradient
wells approximate background water quality (pre-landfill conditions) in the channel and overbank
deposits.
In the late 1990s downgradient groundwater quality began to deteriorate significantly.
This trend included rapidly increasing concentrations of contaminants and leachate indicators in
compliance wells [See Figures 8, 9, 10 and 11]. Concentration trends of most constituents in
most wells appear to have flattened in the last 6 to 10 years, and VOC concentration trends (not
shown on the figures due to very low concentrations) have been relatively unchanged over the
last 10 years.
After performing a routine review of Lakeside‟s annual environmental monitoring reports, DEQ
informed Grabhorn Inc. in an August 2004 letter that: “The data indicates that contaminant
levels and indicator parameters in several compliance wells are exhibiting upward trends and
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that in recent years various permit specific limit concentration2 have been exceeded,
consistently.” The data also indicated that numerous groundwater contaminants exceeded
surface water screening level values and/or ambient water quality criteria; threshold contaminant
concentrations considered protective of aquatic organisms and aquatic habitat. The contaminants
included: ammonia, chloride, calcium, iron, magnesium, zinc and the hazardous substances
barium, manganese, and selenium3. In addition, sampling consistently detected various volatile
organic compounds also called VOCs and other hazardous substances including: benzene,
tetrahydrofuran, 1,1 dichloroethane, and tert-butyl alcohol. However, VOCs are not identified as
chemicals of concern at Lakeside due to either very low concentrations relative to aquatic
screening levels or infrequent detections.
DEQ‟s August 2004 letter noted that nitrate exceeded a numerical groundwater quality reference
level standard and maximum contaminant levels for drinking water in the landfill‟s designated
upgradient well and asked Lakeside to develop a work plan and schedule for: 1) investigating
nitrate contamination, 2) determining groundwater action limits, and 3) monitoring surface water
quality. In response to the detection of nitrate at concentrations above its primary water quality
standard in former background well MW-5, Lakeside conducted an investigation to determine
the source and extent of the nitrate in 2005. The investigation included a sampling program of
MW-5, surface water, and direct push borings advanced near up-gradient of well MW-5. An
October 28, 2005 report documented the findings. The investigation concluded that the source of
the nitrate detected in MW-5 was not related to the landfill and the source, although uncertain,
appeared to up-gradient forestry and/or agricultural-related activities occurring of the well.
Beginning in early 2006, nitrate concentrations in monitoring well MW-5 decreased rapidly and
dropped below the water quality standard in 2007.
2 Based on the goal of preserving all groundwater in the state for its highest potential beneficial use ( typically presumed to be drinking water),
PSCLs previously specified in Lakeside‟s permit were human health and aesthetic (i.e. taste and odor) based.
3 It was later concluded that early detections of selenium were spurious and a consequence of bromide interference. However in 2009, several
years after implementing laboratory procedures to eliminate the interference, selenium was again detected above its SLV.
12
3. REMEDIAL INVESTIGATION
The remedial investigation incorporated multiple environmental data sources including: 1) the
results of historical and on-going groundwater and surface water monitoring required under their
solid waste permit, 2) surface water, sediment, and benthic organism studies within the Tualatin
River, 3) evaluation of the existing ET cover, and 4) results of human health and ecological risk
assessments. The Remedial Investigation was based on a conceptual site model that generally
applies to solid waste landfills. The investigation excluded soil sampling based on the presence
of the landfill cover and ambient air monitoring based on the absence of buildings on the landfill.
Each of these elements are summarized below.
3.1 CONCEPTUAL SITE MODEL
At the Lakeside site, construction and demolition debris, tree prunings, various industrial solid
wastes, and clean soil were filled over the top of 37 acres of floodplain and valley floor adjacent
to the Tualatin River. Precipitation, falling directly on the waste exposed in the working face of
the landfill during its years of operation, and infiltrating through what appears to be a poorly
performing ET final cover system, forms a leachate enriched with salts, metals, and organic
compounds. The leachate drains through the waste then mixes with and contaminates shallow
groundwater underlying the landfill. Depth discrete sampling of groundwater at the riverfront
indicated specific conductivity and total dissolved solids (TDS) decreased substantially at depths
greater than approximately 35 feet to 40 feet below ground surface (85 to80 feet above mean sea
level), or approximately 25 to 30 feet into the water table. As contaminated groundwater
emerges from beneath the landfill footprint it flows approximately 50 to 100 feet south before
seeping out into the main channel of the Tualatin River through sediment pores. Based on
hydrogeologic and geochemical conditions, DEQ presumes that attenuation of landfill
contaminants prior to discharge to the Tualatin is minimal.
3.2 COVER EVALUATION
Lakeside‟s solid waste disposal permit required that all landfill waste be covered on both an
interim and permanent basis to prevent nuisance conditions, minimize leachate generation, and
protect groundwater quality. As an alternative to the conventional low permeability soil cap
typically used at construction and demolition landfills, Lakeside capped the landfill with an ET
cover beginning in 1990. Conventional capping technologies rely on layers of soil and grass or
synthetic, impermeable membrane materials to prevent precipitation from infiltrating into the
waste. In contrast, the ET cover functions as a “sponge” to retain rainfall within the cap and then
relies on evaporation and tree/plant transpiration to minimize the volume of water infiltrating the
waste.
13
In 1989, when Lakeside first proposed using an ET cover, such covers were considered an
experimental landfill-closure technology. Since then, ET covers have been demonstrated to be an
effective method of capping landfills in arid and semi-arid climates. Lakeside initially planted
hybrid poplar trees on the cover at a density of one tree per 3.4 square feet. The ET cover
designer, Dr. Louis Licht, projected the tree canopy would close within 4 to6 years and achieve
optimal evapotranspiration rates, and result in approximately 1 inch per year infiltration or less.
Although in some areas of the cover trees have matured and the canopy is closed, over the
majority of the cover planted more than six year ago (anticipated period to reach canopy closure)
tree growth is stunted and tree mortality rates are high. The result, as the aerial photograph in
Figure 12 shows, is an ET cover with a patchy distribution of trees.
By several measures, the ET cover at Lakeside has not developed as expected; over significant
areas of the cover the original trees have suffered high mortality rates and many of the remaining
trees are stunted showing signs of rodent damage, disease and drought stress. This has resulted
in a cover that is patchy and sparse over significant sections of the landfill cover. The sparse and
patchy tree canopy and evidence of rodent damage, disease, and drought stress observed in the
living trees indicate the cover is not performing optimally to prevent leachate generation and the
associated groundwater contamination. Other potential problems include landfill gas, soil quality
and permeability/compaction and the reliance on deciduous trees that are dormant during the
rainy season and active during the dry season. In particular, poplars may not be well-suited to the
consistently dry summers and falls characteristic of this region. Lakeside subsequently
experimented with planting other tree species on the cover including willow and hybrid and
native Ponderosa pines to identify ones with characteristics more conducive to maintaining an
effective ET cover. Additional ongoing development and testing will correlate tree health to the
cover soil conditions.
At unlined landfills such as Lakeside the cover is the primary engineered feature preventing
groundwater contamination. The deteriorating groundwater quality at Lakeside suggests the
cover is inadequately controlling leachate generation. In 2005, DEQ requested Lakeside evaluate
the cover as part of the remedial investigation. In 2006, Lakeside installed six borings within
areas of the landfill that had received final cover to collect data on cover thickness, soil
permeability, and soil moisture content. The intent of this work was to evaluate the cover soil
characteristics with respect to maintaining an optimally functioning ET cover and to gather semi-
quantitative data that could be used to infer cover performance with respect to deep infiltration
rates. The six cover borings were later modified into 5 feet deep landfill gas monitoring wells. In
2007, Lakeside installed 4 landfill gas observation wells into the waste fill. The depth of the
observation wells range from 36 feet to 44 feet bgs and have 25-foot long screen completed in
waste fill. In 2008, Lakeside installed 6 soil gas probes adjacent to the landfill. The depth of
these soil gas probes range from 10 feet to 35 feet bgs. These investigations, and several others
conducted under the feasibility study, will provide information to assess and enhance the cover.
3.2.1 Cover Evaluation Results
The results of Lakeside‟s 2006 evaluation indicate the soil cover ranged from 1.5 feet to more
than 17 ft thick with an average thickness of more than 10 feet. For comparison, four feet of
cover soil was identified as minimum thickness necessary to store incident precipitation during
14
the trees dormant winter season. The average soil thickness appears adequate for the ET cover
design. In the areas where drilling identified thin cover, Lakeside has since added additional
material so that the cover thickness exceeds the minimum in all areas.
Permeability measurements collected by Lakeside at six locations indicate the 1 x 10-5
cm/sec
permeability requirement4 (applicable to conventional soil covers) was exceeded at three of the
locations with a maximum measurement of 1 x 10-3
cm/s. Since the ET cover does not meet the
low-permeability soil-cover specifications, it must rely on evapotranspiration as the primary
mechanism for minimizing leachate production. DEQ has been concerned that these more
permeable soils may not provide adequate moisture storage and retention to support tree growth
and may contribute to the drought stress observed in portions of the cover.
Soil moisture content was another parameter measured during the cover evaluation completed in
2006. The purpose of collecting this data was to construct soil moisture profiles and to determine
the “net” performance of the ET cover. Irrespective of the more indirect measures of the cover‟s
adequacy (i.e. permeability, thickness, etc.) are the combination of soil characteristics and ET
processes effectively preventing deep infiltration of percolating precipitation. The results of the
data collection found moisture levels at the base of the cover ranged from 70 to100 percent
saturation. These levels of saturation, measured in July of 2006, exceed the soil‟s field capacity
and indicate the cover was not effectively preventing moisture from infiltrating into the
underlying landfill waste. Additional testing and analysis being conducted under the feasibility
study will provide information to assess limitations of the cover and to develop measures to
enhance its performance.
In 2007, Lakeside began a study of landfill gas and oxygen concentrations within the cover. The
purpose was to gain a greater understanding of methane distribution and to characterize
conditions in the cover with respect to supporting tree growth. Six soil gas monitoring wells were
installed to a depth of 5 feet and monitored for methane and major gases. These six cover well
points constructed to measure in situ permeability as part of the cover investigation completed in
2006. The well points were subsequently modified and used to measure for the presence of
landfill gas. In five of the points average methane and carbon dioxide concentrations ranged
from 10-52 percent, and 13-38 percent, respectively. An important observation was that the
oxygen level in 5 of the 6 points was 0.0 percent for extended periods. This suggests that landfill
gas displacement of oxygen may be significantly retarding tree growth and contributing to high
tree mortality. Recent monitoring (2010) indicates that gas concentrations decrease and oxygen
concentrations increase in the upper several feet of the soil cover (See Section 3.6.1). Lakeside is
conducting additional testing to correlate tree health with the presence of landfill gas.
4 Permeability is a measure of the soil‟s ability to transmit fluids. The cited values equate to rates water will percolate downward through a
saturated soil.
15
3.2.2 Cover Evaluation Conclusions
The data collected confirmed the existing ET cover is not performing as designed and is likely
not sufficiently effective in preventing surface water infiltration through the cover and into the
waste. Lakeside and DEQ concluded additional study is necessary to more conclusively
determine the causes of tree mortality and identify remedies to improve cover performance. The
testing is ongoing.
3.3 GROUNDWATER
3.3.1 Plume Dimensions
At Lakeside all groundwater monitoring wells and piezometers are located along the landfill
perimeter. No groundwater monitoring wells are located within the landfill footprint. Absent
such wells, there is no effective means to identify specific source areas within the landfill that
may contribute to the groundwater contaminant plume. However, considering the existing
cover‟s ineffective performance, DEQ presumes that the entire landfill contributes
contamination.
Data indicates upgradient well UG-1 is uncontaminated (except for nitrate, the source of which is
likely upgradient agricultural activities), thus the contaminant plume is inferred to be less than
2400 feet long. At the Tualatin River, the plume‟s width (transverse to the direction of
groundwater flow) is approximately 1500 to 1600 feet, roughly 10 to20 percent greater than the
width of the landfill. Groundwater sampling from monitoring wells near the river and
reconnaissance borings indicate the vertical distribution of chemicals of interest. Depth-discrete
sampling at two locations downgradient of landfill in 2006 indicates specific conductivity and
total dissolved solids decrease substantially at depths greater than 35to 40 feet below the ground
surface, or about 20 to 30 feet into the water table. These measurements are indicators of the
depth of landfill related impacts. [See Figure 13].
The approximate “locality of the facility” is shown in Figure 6. Although the plume is located
mainly within the landfill boundaries, groundwater along the landfill‟s western margin appears to
flow in a southwesterly direction relative to the rest of the shallow groundwater system and the
contaminant plume. This flow pattern tends to push contaminated groundwater westward beneath
private agricultural land. An area mapped as wetlands5 by the U.S. Fish and Wildlife Service lies
downgradient of the groundwater plume‟s southwestern lobe. A flow analysis conducted by
Lakeside as part of the remedial investigation asserted groundwater flowing beneath the landfill
does not migrate to the wetland to the west. These findings have not been verified in the field
and are inconsistent with groundwater monitoring results that indicate the presence of landfill-
related contamination in piezometer P-2, the closest monitoring point located upgradient of the
wetland. Water quality data collected from P-2, suggests the wetland may be within the LOF of
the landfill. DEQ previously requested Lakeside to collect field data to determine the extent of
5 Figure x, adapted from the National Wetland Inventory, U.S. Fish and Wildlife Service. www.fws.gov/nwi/
16
the off-site plume and validate their model of shallow groundwater flow. DEQ expects Lakeside
to conduct additional monitoring and investigation under the remedial design and remedial action
to clarify hydrology in this part of the site.
3.3.2 Plume Chemistry
Total dissolved solids, alkalinity, hardness and chloride levels are significantly elevated in
groundwater relative to natural background (typically an order of magnitude higher). Redox
conditions are depressed and dissolved oxygen levels are depleted. The plume also exhibits
elevated concentrations of ammonia, metals, phosphorus, total organic carbon and trace to
moderate levels of Volatile Organic Compounds (Tables 1 and 2).
VOCs are absent in upgradient (background) groundwater. Consequently, DEQ assumes VOCs
in downgradient groundwater emanate from the landfill. Most VOCs including benzene,
tetrahydrofuran, and 1,1 DCA are consistently detected at trace concentrations and generally near
or below the most stringent human health and ecological risk-based cleanup levels. One
exception is, tert-butyl alcohol which ranges as high in concentration as 300 parts per billion
(ppb) and is more widely distributed throughout the compliance well network than other VOCs.
There have been sporadic detections of semi-volatile organic compounds such as bis-hexyl-
phthalate in compliance wells. Typically, however, the results are not repeatable and suggest the
source may be lab contamination. In addition, there usually are from 400 to 600 ppb of
undifferentiated organic compounds in groundwater samples. Their nature and source are
unknown, but a portion of these contaminants may relate to non-hazardous organic compounds
such as humic and fulvic acids. Because semi-volatile organic compounds are detected
infrequently at concentrations below risk-based levels, they are not considered to be chemicals of
concern at Lakeside.
Metals such as iron, magnesium, manganese and zinc occur naturally and detectable levels are
present in the background/upgradient well UG-1. However, as groundwater passes beneath the
landfill, mixes with landfill leachate, and reaches the downgradient compliance wells these
metals increase greatly in concentration, many by a factor of 10 or more (See Table 3).
Detections of selenium have varied over time, and sometimes exceed DEQ‟s screening level and
EPA‟s national recommended ambient water quality criterion of 5 ppb. However, the observed
levels are near the analytical method‟s quantification limits and there have been some spurious
detections of selenium previously reported at Lakeside that were later determined to have been
caused by chemical interference. Mercury has been detected in only one sample since 2005 at a
concentration just above the reporting limit and at a concentration less than the ecologic
screening level.
DEQ assumes the metals detected in groundwater at Lakeside‟s compliance wells have two
sources, the landfill waste itself and the native soils the waste was placed on. Under natural
conditions, metals are primarily bound up in minerals present in the soil that are only slightly
soluble in groundwater. However at Lakeside, landfill leachate has altered the groundwater
geochemistry by depleting oxygen and creating chemically reduced conditions. Under reducing
conditions otherwise immobile metals become more soluble and mobile and their concentration
17
increases in groundwater. The same mechanism has mobilized metals within the landfill waste
itself.
3.3.3 Other Contaminants and Physiochemical Conditions
Barium, calcium, and ammonia concentrations in compliance wells significantly
exceed background levels. The Tualatin is water quality limited for dissolved
oxygen from May through October, and TMDLs have been established for
ammonia as it relates to oxygen depletion.
Cyanide concentrations sporadically exceed the ambient water quality criteria for
free cyanide (the most toxic form of cyanide). Cyanide‟s toxicity varies greatly
depending on its chemical state. At Lakeside, the cyanide‟s chemical form is
unknown.
Phosphorus concentrations in compliance wells also exceed background levels.
Although slow seepage rates limit the Tualatin River‟s mass loading by
contaminated groundwater, phosphorous concentrations typically exceed DEQ‟s
TMDL (background concentration) for the Tualatin of 0.17 mg/L.
In 2007 Dissolved oxygen levels in UG-1 averaged 6.6 mg/l. ODEQ Table 21
Dissolved Oxygen & Intergravel Dissolved Oxygen Criteria (2/22/07) indicates 6.5
milligrams/liter dissolved oxygen provides optimal conditions for supporting cool
water aquatic habitat. DEQ has characterized as “cool water” aquatic habitat the
Tualatin reach that includes Lakeside. Lakeside‟s background water quality
indicates that natural DO levels will support the river‟s cool water habitat.
However, as groundwater passes beneath the landfill and mixes with leachate,
dissolved oxygen levels decline and become significantly depressed. The result is
anoxic groundwater with high chemical oxygen demand. DO levels in MW-3, MW-
8, and MW-10 in 2007 averaged 0.9 milligrams/liter, 1.1 milligrams/liter, and 1.2
milligrams/liter, respectively. As indicated in Table 3 the dissolved oxygen levels in
riverfront wells are below the threshold required to support cool water aquatic
habitat.
Lakeside‟s low dissolved oxygen in groundwater is associated with high chemical oxygen
demand levels. This chemical-affected groundwater represents an oxygen sink to the aquatic
environment. Since 2008, chemical oxygen demand averaged less than 5 milligrams/liter in up-
gradient well UG-1, as compared to 236 milligrams/liter, 230 milligrams/liter, and 392
milligrams/liter in down-gradient wells MW-3, MW-9 and MW-10, respectively. Note: historic
highs have been as great as 500 mg/l along river front wells. For comparison, chemical oxygen
demand in untreated domestic wastewaters range 250 to1000 mg/l (Metcalf and Eddy, 1991).
18
3.4 CONTAMINANT FATE AND TRANSPORT
Lakeside‟s downgradient monitoring wells are located 35 to 75 feet from the Tualatin River.
Considering this small separation distance and the hydrogeological and geochemical
environment along the plume‟s transport pathway, DEQ concluded that most contaminants
undergo minimal attenuation before entering the river‟s shallow sediment benthic environment.
3.4.1 Chemical Attenuation
As observed during the Lakeside remedial investigation and documented by the USGS and
others, the Tualatin‟s sediment environment is highly reducing. Under these oxygen deficient
conditions many of the contaminants mobilized by reducing conditions (i.e. arsenic, iron,
manganese, zinc) in and beneath the landfill are unlikely to precipitate out of groundwater along
its flow path to the river. VOCs such as tetrahydrofuran tend to be more persistent under
reducing conditions and are also expected to migrate the relatively short distance to the river.
Chloride, a stable, highly soluble anion is also expected to enter the benthic environment
relatively unchanged, because chloride transport is not chemically attenuated by any known
natural mechanisms.
3.4.2 Mixing and Dilution
Mixing and dilution of contaminated groundwater is not anticipated to be a significant
attenuation mechanism at Lakeside. USGS and Lakeside estimates of groundwater flux rates at
the downgradient boundary of the landfill, when compared to estimated seepage rates through
the channel bottom, suggest most of the water discharged to the Tualatin River along the landfill
reach consists of leachate contaminated groundwater. Furthermore, the strong upward hydraulic
gradient within river sediments observed by the USGS indicates there is minimal mixing of
groundwater with surface water before it reaches the benthic environment.
3.5 SURFACE WATER
3.5.1 Tualatin River
Between 2004 and 2006, Lakeside collected samples of river water to determine if contaminated
groundwater discharges were impacting the Tualatin‟s water quality. In the fall of 2004 and in
the spring and summer of 2006 Lakeside sampled the river at four locations [See Figure 7]
adjacent to the landfill. This effort provided data on site contaminant concentrations in the river
water-column for a range of river flow conditions.
The testing results indicated that downstream concentrations of calcium, magnesium, iron, and
manganese consistently exceeded upstream concentrations by 10 to45 percent. Concentrations of
barium and ammonia, were essentially uniform along the landfill reach while zinc levels
consistently declined over this section of the river. Ammonia and barium exceeded ambient
water quality criteria and/or DEQ screening level values during two of the monitoring events and
manganese exceeded these criteria during one monitoring event. All other compounds were well
below their respective aquatic screening levels.
19
Discussions with US Geological Survey staff (Stuart Rounds, August 22, 2008) confirmed that:
1) the Tualatin River‟s water quality near Lakeside varies unpredictably over short times frames,
and 2) The Rock Creek wastewater treatment plant discharges strongly influence the river‟s
overall water quality. Because of these conditions, it is difficult to determine how possible
discharges of contaminated groundwater might impact surface water quality. Moreover, the
treatment plant effluent is the likely the predominant source of the river‟s elevated ammonia
concentrations. After evaluating these conditions and observations, DEQ allowed Lakeside to
discontinue their surface water sampling program.
Available data indicates that most landfill contaminants have acceptable levels within the river‟s
surface water column. Ammonia and barium are exceptions, but DEQ does not attribute their
uniformly elevated concentrations along the landfill reach to landfill impacts. Manganese is the
only element with downstream concentrations that are significantly elevated relative to upstream
concentrations and which also exceed DEQ ecologically-based screening level values for
surface water. The following qualifiers should be considered when evaluating surface water
data collected at Lakeside:
All sampling points were potentially within the influence of the landfill and contaminated
groundwater discharges. Consequently, upstream/baseline conditions may be represented
inaccurately and associated conclusions lack certainty.
The Remedial Investigation did not evaluate the vertical or lateral distribution of
contaminant levels within the Tualatin River water column.
The data does not reflect pore-water chemistry and conditions within the benthic
environment.
The primary environmental concern related to groundwater contamination from Lakeside is its
potential adverse impact on aquatic organisms, particularly those inhabiting the Tualatin River‟s
channel sediments (benthic environment) and nearby wetlands. Another concern is that
contaminated groundwater emanating from Lakeside is exacerbating the Tualatin River‟s well
documented water quality problems.
3.5.2 Unnamed Creek
In November 2005, Lakeside sampled water from the unnamed creek east of the landfill and
analyzed the samples for ammonia, nitrate, phosphorus, TDS, and several other water quality
parameters. Ammonia was not found in any sample (although nitrogen as nitrate is detected), and
other parameters reflected relatively good water quality conditions. The one exception, nitrate,
was significantly elevated relative to typical surface water concentrations. The highest
concentrations were upstream of the landfill and the concentration trend as the creek approaches
the Tualatin River indicates elevated levels are not related to the landfill.
20
3.5.3 Landfill Seep
In August 2006, Lakeside sampled a seep located near staff gauge SG-1. The results indicate that
landfill contaminants ammonia, barium, iron, and manganese significantly exceeded background
concentrations (based on recent data from UG-1 and past data from MW-5) and their respective
DEQ screening level values.
The sample‟s general chemistry including elevated total dissolved solids, low redox potential,
and depleted oxygen indicate the seep is leachate impacted.
The seep represents a direct, albeit small, discharge of leachate contaminated groundwater to the
Tualatin River.
The ground near the seep was clear of trees and underbrush, and the exposed seep easy to see.
Areas further upstream of the seep are heavily vegetated, potentially obscuring other active
seeps.
3.6 SOIL
The long-term landfill operations involved placing clean cover soils over non-hazardous solid
waste. Therefore, no contaminated soil is anticipated at or near the surface. Furthermore, DEQ
and Lakeside have not observed chronic or perennial landfill-related seeps that would
contaminate surface soils.
3.6.1 Landfill Gas and Methane
The DEQ closure permit requires Lakeside to conduct landfill gas monitoring in soil gas probes
to evaluate the distribution of methane concentrations and pressures in and around the landfill.
The main focus of Lakeside‟s landfill gas monitoring program is to monitor for methane soil-gas
concentrations around the landfill perimeter and near onsite structures.
The gas monitoring network includes six compliance probes located as follows: three probes
(SGP-1, SGP-2 and SGP-3) along the landfill‟s western boundary; one probe (SGP-4) in the
large equipment storage building next to Lakeside‟s shop; one probe (SGP-5) near the landfill
scale house; and one probe (SGP-6) north of the landfill near piezometer P-7. In addition, four
landfill gas observation wells are located within the landfill footprint. These observation wells
provide information about the methane generation rates and gas pressures within the landfill
itself.
Initially, Lakeside monitored the six compliance probes on a monthly frequency to assess gas
generation and migration trends under worst-case winter weather conditions. After establishing
this database and assessing trends, Lakeside reduced the monitoring frequency to a quarterly
schedule. Lakeside‟s compliance monitoring has detected methane in two compliance probes,
SGP-2 and SGP-5. Typical methane concentrations in SGP-2 vary from about 35 percent to
about 47 percent by volume. Although these concentrations greatly exceed the methane
compliance limit of 5 percent by volume (which is a condition of potential concern if there could
be gas migration to structures), static pressures in this probe have been minimal, suggesting low
21
potential for lateral migration in subsurface soils. In addition, SGP-2 is located next to un-
developed property in Lakeside‟s ownership that serves as a buffer to neighboring, developed,
properties.
Methane concentrations in SGP-5 vary from 0 percent to about 16 percent by volume. Although
these methane concentrations also exceed the 5 percentcriterion, and could pose a potential risk
to the existing scale house structure, Lakeside indicates they keep the scale house open to
maintain adequate ventilation.
Methane concentrations in the landfill observation wells (GP-1, GP-2, GP-3, and GP-4) have
been consistent across the landfill and indicative of typical landfill-source conditions (52 percent
to 57 percent methane by volume). Static pressures have been low at these wells suggesting that
overall landfill gas generation rates also are relatively low. The landfill‟s high internal methane
concentrations, though, may adversely impact tree growth and survival on the ET cover.
Attempts to enhance the ET cover‟s tree growth and performance must consider and potentially
mitigate landfill gas related impacts.
3.7 TUALATIN RIVER SEDIMENT
3.7.1 Sediment Chemistry
In February 2009, Lakeside sampled sediment from three separate river reaches approximately
1400 feet in length. Lakeside collected forty-four grab samples at about 100 feet intervals in 10-
19 feet of water between the north river bank and the center of the channel. These samples were
analyzed for site contaminants ammonia-nitrogen, barium, calcium, chloride, magnesium,
manganese, and zinc. Review of the data indicates that concentrations of some constituents
(ammonia, barium, chloride and manganese ) where higher in sediments from the landfill and/or
downstream reaches than in sediments from the upstream (reference) reach, but except for one
case, the differences were not statistically significant, and it is not clear whether any differences
are caused by the landfill. Chloride (an anion) in particular may not be readily attenuated in
localized areas.
When Lakeside submitted its Tualatin River Sediment Sampling report to DEQ, sediment
ecological screening values to protect aquatic organisms existed for iron, manganese and zinc.
The iron concentration exceeded its sediment SLV in the upstream and downstream reaches.
Manganese exceeded its screening level value in the downstream reach only.
Overall, within the landfill and downstream reaches there appeared to be some increase in
landfill related contaminants in sediments relative to samples collected within the upstream
reference/baseline reach. In particular, DEQ considers the detection of chloride along the landfill
reach as evidence that contaminated groundwater is reaching the benthic environment
(biologically active zone) relatively un-attenuated. Chloride was observed at concentrations up to
210 milligrams per kilogram in sediment sampled along the landfill reach of the river. DEQ
calculated a chloride concentration in sediment pore water assuming the chloride was dissolved
in water consistent with chloride‟s chemical properties and the sediment‟s origin and
characteristics. DEQ calculated chloride concentrations in pore water were consistent with
22
levels measured in groundwater compliance monitoring wells located near the river, which
exceed ambient water quality criteria of 230 milligram/liter.
3.7.2 Benthic Macroinvertebrate Survey
In the summer of 2007, Lakeside conducted a benthic macroinvertebrate bioassessment study as
an alternative to a porewater study to determine if macroinvertebrate (i.e. aquatic insects, worms,
freshwater shellfish) communities located adjacent to and downstream of Lakeside differed from
upstream communities. The sampling included two approaches: fixed-area, sediment grab
samples; and fixed-time samples. The fixed-area sediment grab samples were collected at
random locations along a fixed transect established in each of the five reaches studied. The fixed-
time samples used a fixed level of effort (30 minutes) to sample common microhabitats present
within the study area.
The resulting data showed almost identical macroinvertebrate populations in each of the reaches
studied. The results of this investigation do not indicate that activities associated with the
Lakeside Landfill are affecting invertebrate assemblages in aquatic habitats located adjacent to,
or directly downstream of the Landfill, as compared to upstream conditions. The survey,
however, also concluded that the river‟s macroinvertebrate populations consisted mostly of
“pollution tolerant” to “highly pollution tolerant” species that reflect a highly degraded habitat.
DEQ concluded the widespread degradation rendered the benthic invertebrate study inconclusive
and not useful for determining if the landfill has impaired the shallow groundwater‟s recognized
beneficial use (sustaining aquatic habitats). Subsequently, DEQ informed Lakeside that
groundwater/pore water chemistry should be the sole basis for such a determination.
3.7.3 Ambient Air
The low level of VOC concentrations detected in groundwater monitoring wells at Lakeside are
well below conservative DEQ screening levels developed to protect outdoor air quality.
Consequently, DEQ has not required Lakeside to conduct ambient air sampling.
3.8 RISK ASSESSMENT
Lakeside‟s risk assessment results for human health and potential ecological receptors are
summarized below. More detail is available in Level I Scoping Ecological Risk Assessment,
Lakeside Reclamation Landfill, URS, 2007; Screening-Level Human Health Risk Assessment &
Level II Screening Ecological Risk Assessment, URS/Parametrix, 2009 ]. The residual risk
assessment for the recommended remedial action alternative is summarized in Section 6.2 of this
document.
3.8.1 Human Health Risk Screening
The human health risk screening was based on the conceptual site model and land and water use
identified in the vicinity of the landfill (see Sections 3.1 and 2.4). Groundwater, surface water
and sediment were the media where human exposure could occur. Since the Tualatin River has a
beneficial use for fish consumption, this pathway was also considered a potentially complete
exposure pathway.
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The risk assessment used the following three criteria to identify chemicals of concern at
Lakeside: 1) frequency of detection, 2) exceedence of background concentrations and, 3)
exceedence of a risk-based concentration. Based on these criteria, arsenic, benzene and zinc were
identified as chemicals of concern. First, the contaminant concentrations for each environmental
medium were compared with conservative risk-based screening level values to determine which
media and contaminants posed potential risk to human health.
If concentrations of chemicals detected in a particular medium did not exceed the screening
levels, that medium was eliminated as a medium of potential concern and was not evaluated
further. Chemicals and pathways that exceeded the screening levels were carried through for
detailed evaluation in the baseline risk assessment. The risk assessment evaluated contaminant
concentrations in groundwater based on data collected between April 2004 and July 2007.
A brief summary of the results for each environmental medium is provided below:
Sediment – No sediment samples exceeded human health screening levels.
Solid Wastes – The landfill‟s typical operating procedure (consistent with permit
conditions), involved placing clean cover soils over non-hazardous solid waste.
Therefore, DEQ does not expect contaminated soil to be present at or near the surface.
Furthermore, no chronic or perennial groundwater seeps that could contaminate surface
soils have been observed on the landfill.
Methane monitoring in the form of soil gas sampling has been conducted by Lakeside to
evaluate the distribution of methane concentrations and pressures in and around the
landfill. The monitoring results indicate that no onsite structures, offsite properties, or
offsite structures are currently at risk from methane migration. Considering the high
methane concentrations within the landfill, however, and the unpredictability of landfill
gas migration, the DEQ closure permit requires Lakeside to continue methane
monitoring indefinitely and re-evaluate the program periodically to assure that
conditions remain safe.
Surface Water – No Contaminants of Interest (COIs) were detected in surface-water
samples at levels that exceeded applicable screening levels.
Bioaccumulation and Fish Ingestion - The risk assessment completed by URS
dismissed the potential fish-ingestion pathway based on assumed significant dilution
and attenuation occurring in the water column.
Groundwater - Lakeside‟s human health screening indicated the arsenic groundwater
concentrations exceeded the screening level for trench worker direct contact exposure
due to an error in concentration units. However, the actual DEQ screening level is 5.8
milligrams/liter or a factor of 1000 higher than the level used in the risk screening.
Arsenic concentrations in groundwater have never been above the screening level.
Consequently, this pathway does not lead to unacceptable risk for worker exposure.
24
Site groundwater exceeds EPA tap water regional screening levels for the following
contaminants: arsenic, benzene, iron, manganese, and zinc. Tert-butyl alcohol is
another groundwater contaminant of concern. Although EPA and DEQ have not derived
regulatory or risk-based screening levels for tert-butyl alcohol, the California Health
Hazard Assessment established a notification level of 12 micrograms/liter for this
contaminant. Lakeside‟s groundwater concentrations of tert-butyl alcohol consistently
exceed California‟s notification level.
Hydrogeologic conditions and historic patterns of groundwater use indicate
groundwater contaminants emanating from the landfill will not affect domestic or
agricultural supply wells located in the vicinity of the site. As indicated by a
comparison of static water levels in wells completed into the Columbia River Basalt
and shallow groundwater monitoring wells completed at the site, shallow groundwater
within the valley fill sediments are not hydraulically connected to the water-bearing
zones within the Columbia River Basalt group preventing contamination from migrating
into these aquifers. Hydraulic gradients within shallow groundwater occurring beneath
and downgradient of landfill further prevent deep migration of contamination and
isolate shallow groundwater from the productive aquifers of Columbia River Basalt
group. Consequently, DEQ has concluded groundwater within the Columbia River
Basalt group is outside (or more appropriately, below) the site locality of facility.
To summarize, Lakeside‟s risk assessment carried forward and evaluated specific chemicals and
media that exhibited complete risk pathways. Accordingly, Lakeside screened out arsenic,
benzene and zinc from the groundwater pathway. The remaining media and chemicals did not
exceed acceptable human-health risk levels and were dropped from any further assessment. A
conceptual site model for human health exposure to site contaminants is presented in Figure 14.
Based on the above analysis and site conditions, DEQ concludes that the site does not pose
unacceptable human health-risks to site-related contaminants.
3.8.2 Ecological Risk Assessment
The ecological risk assessment was completed in accordance with Oregon Department of
Environmental Quality, Guidance for Ecological Risk Assessment, April 1997. Lakeside
conducted a level I ERA in 2007 (URS/Parametrix, 2007) that indicated further assessment was
necessary. In response, Lakeside submitted a draft Level II ERA in December 2007 and a revised
Level II ERA in July 2009. The ERA screened Chemicals of interest for their potential impacts
to ecological receptors by comparing site concentrations measured at downgradient compliance
points to generic screening criteria. This process identified chemicals of potential ecological
concern. The screening method used maximum detected concentrations of contaminants in
relevant media to assess potentially unacceptable risks to stationary biota (i.e. freshwater clam)
and compared the 90 percent upper confidence limit of the mean contaminant concentrations to
screening criteria for mobile aquatic receptors. The ratio of the exposure point concentration to
the aquatic standard or screening level value depicts the degree of impairment or adverse
ecological impacts. This ratio is defined as a hazard quotient. A hazard quotient exceeding one
indicates a potential significant risk to ecological receptors from exposure to that compound. The
sum of the hazard quotients provides a measure of overall toxicity posed to the ecological
25
receptor. Some contaminants have hardness-dependent toxicity. The concentrations of such
contaminants were adjusted consistent with EPA guidance (EPA, 2006c (ERA), Appendix B)6.
The risk assessment also considered general water quality parameters associated with landfill
leachate-impacted groundwater to determine potential effects on the Tualatin River‟s ecological
receptors. This list of parameters, referred to as physiochemical parameters, includes: total
dissolved solids, dissolved oxygen, phosphorus, chloride, pH, temperature and specific
conductance.
3.8.2.1 Chemicals of Concern.
The chemicals of ecological concern at Lakeside are: ammonia, barium, calcium, chloride, iron,
magnesium, manganese and zinc [See Table 4]. Additional chemicals without established SLVs
will also be monitored.
3.8.2.2 Physiochemical Conditions of Concern
Because this reach of the Tualatin River is classified as “cool water habitat” and total maximum
daily loads (TMDLs) are established for the Tualatin, the risk assessment also evaluated the
impact of dissolved oxygen and phosphorus levels in groundwater.
3.8.2.3 Pathway Analysis
The exposure pathway for ecological receptors results from contaminated groundwater
discharging to surface water [See Figure 15]. Groundwater concentrations are assumed to be
undiluted as they enter the river‟s benthic environment (e.g. porewater concentrations are equal
to groundwater concentrations measured at riverfront compliance wells).
Although certain contaminants exceeded their respective aquatic screening level values, the
distribution of chemical concentrations in sediments does not allow a definitive identification of
the source. Furthermore, the magnitude of the impacts does not indicate a need for remedial
action. Based on these factors, DEQ is not requiring additional sediment sampling at this time.
3.8.2.4 Cumulative Risk.
Cumulative ecological risks are summarized in the Table 5. Contaminants in groundwater with a
hazard quotient significantly exceeding one, which is the threshold for potential toxicity, include
ammonia-nitrogen, barium, calcium, chloride, iron, manganese, and zinc. The cumulative sum
of the hazard quotients is 395, indicating sediment dwelling organisms are likely to be harmed if
exposed to groundwater discharging through the river‟s sediment bed.
6 Typically, the hardness referred to in these calculations is that of the receiving water not the discharging water as was done by URS. However,
the conceptual site model indicates groundwater is unmixed with surface water as it enters the benthic environment, therefore, modifying hardness dependent concentrations based on the discharging water chemistry is appropriate.
26
3.9 IDENTIFICATION OF HOT SPOTS
The criteria used to evaluate remedial alternatives for groundwater and surface water depend on
whether a “hot spot” is present or not, as determined by a loss of “current or reasonably likely
future” beneficial use of the water resource.
OAR 3401-122-115(9) defines beneficial uses of water as:
Any current or reasonably likely future beneficial use of groundwater or surface water by humans or
ecological receptors.
OAR 340-122-115(32) defines hot spot of contamination as:
(a) For groundwater or surface water, hazardous substances having a significant adverse effect on beneficial uses of
water or waters to which the hazardous substances would be reasonably likely to migrate and for which treatment is
reasonably likely to restore or protect such beneficial uses within a reasonable time, as determined in the feasibility study; and
(b) For media other than groundwater or surface water, (e.g., contaminated soil, debris, sediments, and sludges;
drummed wastes; "pools" of dense, non-aqueous phase liquids submerged beneath groundwater or in fractured bedrock;
and non-aqueous phase liquids floating on groundwater), if hazardous substances present a risk to human health or the environment exceeding the acceptable risk level, the extent to which the hazardous substances:
(A) Are present in concentrations exceeding risk-based concentrations corresponding to:
(i) 100 times the acceptable risk level for human exposure to each individual carcinogen;
(ii) 10 times the acceptable risk level for human exposure to each individual noncarcinogen; or
(iii) 10 times the acceptable risk level for exposure of individual ecological receptors or populations of ecological
receptors to each individual hazardous substance.
(B) Are reasonably likely to migrate to such an extent that the conditions specified in subsection (a) or paragraphs (b)(A) or (b)(C) would be created; or
(C) Are not reliably containable, as determined in the feasibility study.
The shallow groundwater system located beneath the southern half of the landfill and extending
to midline of the Tualatin River channel is a potential hot spot. At this location, groundwater
contaminant concentrations exceed levels considered protective of aquatic organisms and
adversely impact the beneficial use of groundwater (sustaining aquatic habitat). A hot spot of
contamination is defined in OAR 340-120-115(32). The approximate location of the groundwater
hot spot is described in Figure 16. Figure 16 approximates the hotspot area based on an
interpolation and extrapolation of available groundwater quality data. The hotspot boundaries
will be further refined based on additional groundwater data collected during the remedial design
phase of the project.
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4. DESCRIPTION OF REMEDIAL ACTION ALTERNATIVES
This section describes the remedial action objectives, protective levels and regulatory requirements
or considerations used in developing the remedial action alternatives to address the unacceptable
risk posed by shallow groundwater contamination discharging to the Tualatin River. The evaluation
of the alternatives follows in Sections 5 and 6.
4.1 REMEDIAL ACTION OBJECTIVES
DEQ developed acceptable risk levels, as defined in OAR 340-122-115(1) through (6), and
remedial action objectives based on the identified beneficial uses, exposure pathways and the
risk assessment.
4.1.1 Risk Based Concentrations
DEQ established risk-based concentrations and screening level values (See Table 6) in
micrograms per liter (parts per billion) for groundwater and surface water to protect the
identified beneficial uses and potential receptors. These are considered preliminary remedial
action levels that may be modified based on one or more of the following: 1) water hardness
(according to Table 20 guidance), 2) temperature and pH (according to guidance presented in
EPA-822-R-99-014), and/or 3) site-specific background water quality data.
4.1.2 Remedial Action Objectives
DEQ developed site-specific remedial action objectives (RAOs) for landfill cover performance
and groundwater cleanup. OAR 340-122-040 requires the RAOs to protect human health,
ecological receptors, and beneficial uses. The RAOs for the site are as follows:
RAO #1 - Prevent further degradation of groundwater quality beneath the landfill
RAO #2 - Protect the Tualatin River‟s surface water beneficial uses by preventing current
or future discharge of contaminated groundwater that would result in violations of
ambient water quality criteria, total maximum daily load, or applicable risk-based criteria.
RAO#3 - Treat the groundwater hot spot of contamination to the extent feasible, as
specified in OAR 340-122-090(4).
4.2 GROUNDWATER PLUME AREA AND VOLUME
The area of potential groundwater contamination subject to remedial action is approximately 60
acres, with an estimated volume of 1.7 million cubic feet.
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4.3 APPLICABLE REQUIREMENTS
The following regulations were identified by DEQ in the evaluation of the FS and development
of the proposed remedial action for the facility:
4.3.1 Oregon Solid Waste Management (ORS 459 and OAR 340-93 and 340-95).
This statute and implementing rules govern the management of solid wastes, including the
permitting of disposal sites, and are applicable to the off-site management of contaminated soils
that are not hazardous wastes.
4.3.2 Oregon Water Pollution Control Act (ORS 468B).
This act and the implementing administrative regulations (OAR 340-45) govern discharge of
pollutants to surface waters. The act incorporates the federal Clean Water Act programs
including the National Pollution Discharge Elimination System (NPDES) permitting program.
These regulations would be applicable to any alternative involving discharge of treated
groundwater to the Tualatin River. Pursuant to OAR 340-045-0062, the DEQ may issue an order
in lieu of to an NPDES permit, or exempt the NPDES permit requirement under ORS
465.315(3).
4.3.3 Oregon Water Quality Standards (ORS 468B and OAR 340-41).
The state-wide water quality management plan under OAR Chapter 340, Division 41, specifies
beneficial uses, policies, standards and treatment criteria for Oregon. These standards protect
aquatic life and public health, and are applicable to the site as recharge to the Tualatin River is
one of the beneficial uses of groundwater. Beneficial uses specified in these rules were used in
the identification of remedial action objectives and groundwater cleanup levels for the facility.
4.3.4 Oregon Groundwater Quality Protection Act (ORS 468B).
This act and the implementing administrative regulations (OAR 340-40) constitute Oregon's
groundwater protection program. The program incorporates federal Safe Drinking Water Act
requirements and maximum contaminant level (MCL) standards. The groundwater protection
program policy states that the rules are not to be used as cleanup standards, but they may be used
to evaluate non-degradation of existing groundwater resources subject to the requirements of
Lakeside‟s closure permit. The groundwater protection act would apply to land application of
extracted groundwater.
4.4 LANDFILL COVER REMEDIAL ACTION ALTERNATIVES
Candidate technologies to address RAO #1, infiltration control to restore groundwater quality
beneath the landfill, include 1) no action, 2) replacement of the existing cover with an
impermeable membrane, and 3) enhancement of the existing ET cover. All remedy components
will be subject to performance monitoring and complemented by the Adaptive Management
Program (See Section 7.2).
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4.4.1 Alternative 1: No Action
The landfill‟s existing ET cover consists of patchy stands of poplars, willows and conifers. The
trees range in age (years since planted) from 1 to 21 years old. Much of the landfill cover was
recently closed and planted with young poplar and pine trees in 2010. The older distressed stands
of trees and the newly planted areas leave much of the landfill footprint devoid of tree cover.
Under this no-action alternative the existing ET cover would not be modified or enhanced.
No action would be taken to augment or enhance the existing ET cover or improve cover
performance. This alternative does nothing to reduce current or future rates of infiltration,
leachate generation, or mitigate existing groundwater contamination beneath the landfill.
The total projected cost of this remedy alternative is $2 million, which represents the cost for
maintaining the ET cover as required under the landfill closure permit.
4.4.2 Alternative 2: Impermeable Cap
Modern municipal solid waste landfills commonly are capped with an impermeable
geomembrane barrier layer to prevent or minimize infiltration of precipitation into the underlying
waste, thus limiting the production of leachate. A typical MSW landfill cap is multi-layered
consisting of a gas-venting layer, a low permeability barrier layer (i.e. compacted soil,
geosynthetic clay liner and/or a geomembrane), a drainage layer, and a vegetated top-soil layer.
Construction of an impermeable cap would require complete removal of the existing vegetative
cover and regrading of the cover surface. The existing mixture of trees, shrubs and grasses would
likely be replaced with a mono crop of shallow rooting grasses. Construction of an impermeable
cap would eliminate pathways for landfill gases to vent to the atmosphere. To mitigate gas
buildup and gas migration away from the landfill, an active gas collection system would likely
be incorporated into the cap design and maintained for an indeterminate period. Furthermore,
water storage capacity in the cover, and removal through evapotranspiration would be greatly
reduced compared to the existing ET cover. Installation of an impermeable cap would likely
require construction and operation of a stormwater collection and disposal system.
The estimated total cost of the remedy is $8 million.
4.4.3 Alternative 3: Enhancement of the Existing ET Cover
Properly designed and maintained ET covers can prevent or minimize drainage of precipitation
through the cover and into the waste. An ET cover consists of a layer of soil and mixed
community of grasses, shrubs and trees. Some of the incident precipitation is intercepted by the
vegetation and directly evaporates off of leaves and branches to the atmosphere. The component
of precipitation that does infiltrate the surface is held by the cover soil like a sponge and is
subsequently taken up by the trees through transpiration. Deciduous trees, like the poplars
planted at Lakeside dry out the soil cover in the summer, creating storage capacity in the soil for
water falling as precipitation during the trees dormant winter period. Alternatively, conifers can
be used to provide year round interception and transpiration. The shrubs and trees of an ET cover
30
also provide habitat for wildlife and enhance the aesthetic appearance of the landfill.
Enhancement of the existing ET cover would consist of three phases: 1) additional testing and
surveying to determine tree distribution and health, determine the distribution of landfill gases
and the relationship to tree growth/health, testing of cover thickness and moisture regimes, and
evaluation of alternative tree species; 2) enhancement of the cover to optimize conditions for
native tree species, health, and growth based on the results of phase 1; and 3) conduct cover
performance monitoring, implement adaptive management and verify RAO achievement.
The estimated total cost of the remedy is $2.3 million.
4.5 GROUNDWATER REMEDIAL ACTION ALTERNATIVES
The FS screened response actions and remedial technologies to address RAO #2, protection of
the Tualatin River. The list of general response actions included groundwater containment,
extraction, and treatment, and in-situ treatment. The FS evaluated several remedial technologies
for each general response action and developed remedial action options from viable response
actions and technologies that can meet the RAOs.
Remedial action alternatives 2a, 2b, 3, and 5 include extraction of contaminated groundwater at
rates initially estimated at approximately 20,000-25,000 gallons per day. The Feasibility Study
discusses several options for treating and reusing this water7. DEQ reviewed the technology
alternatives and preliminarily selected a treatment/reuse option based on the same balancing
factors used in the remedy selection process. For clarity, DEQ included its evaluation of the
feasibility balancing factors for groundwater treatment and/or disposal option in Section 5.3
Disposal or reuse of treated groundwater would be considered on-site for purposes of ORS
465.315(3). ORS 465.315 provides that for onsite portions of an approved remedial action no
state or local permit, license or other authorization will be required for, and no procedural
requirements will apply, although substantive requirements are not affected. There does not
appear to be substantive state or local legal barriers to the land application of ground water on
the parcels identified in the FS Addendum. Substantive NPDES requirements have not been
determined for discharge of treated groundwater to the Tualatin River. Lakeside would be
required to coordinate with local government bodies as to substantive requirements and pay fees
of such bodies as stated in ORS 465.315(3). A remedial action/remedial design work plan will
provide the design basis and details.
This total cost for each groundwater remedial alternative in total net present value cost (2011
dollars) assumes a 2.5 percent annual discount rate8. The total net-present value of the alternative
includes capital costs for construction, operation, maintenance, monitoring, reporting, system
decommissioning and closure, and contingent actions. Cost estimates are generally within plus
or minus 30 percent of the likely costs and are refined after the final remedy design is completed.
7 Although the May 2010 feasibility study does not explicitly break out groundwater treatment and/or reuse options
separately from other components of the groundwater remedy, for clarity DEQ has done so. 8 Note: All remedy cost estimates in this report are expressed as net present values costs that assume a 2.5% annual
discount rate.
31
A description of the groundwater treatment and disposal/reuse alternatives are provided below.
4.5.1 Alternative 1: No Action
Under Alternative 1, contaminated groundwater exceeding criteria for protection of the surface
water beneficial uses (maintenance of aquatic habitat) would be allowed to discharge to the river
unabated.
The total projected cost of this remedy alternative is $1.2 million, which represents the cost for
compliance monitoring required under the landfill closure permit.
4.5.2 Alternative 2a: Groundwater Extraction (Wells), Pretreatment, and Land Application
Under Alternative 2a, a network of approximately 129 extraction wells will be placed within an
area of the groundwater hot spot located between the toe of the landfill and the river to control
groundwater seepage into the river. Pumping down water levels in the extraction wells will
hydraulically reverse the flow direction of contaminated groundwater, preventing groundwater
contaminated above remedial action cleanup levels (RACLs) from discharging to the Tualatin
River. It is estimated that a total groundwater extraction rate of 15 gallons per minute
(approximately 22,000 gallons/day) is required to achieve hydraulic control over the portion of
the groundwater plume exceeding RACL, with each well pumping approximately 1.25 gpm.
Hydraulic control and containment of groundwater can be achieved within hours to days after
pumping begins.
Data collected on groundwater elevations and river stage indicate the typical direction of
groundwater flow (southerly towards the river) reverses seasonally due to high stage conditions
in the Tualatin. This information indicates the network of groundwater extraction wells can be
operated/shut down seasonally and still effectively prevent the plume of contamination from
discharging to the river. The seasonal pumping strategy will be refined during the remedial
design phase and its implementation adjusted based on performance monitoring data.
Initially, extracted groundwater will be routed to a cascade aerator for the primary purpose of
oxidizing iron and manganese into less soluble forms that can be removed through precipitation
and filtration. The aerated water would then be conveyed to two approximately 1000 ft2 lined
emergent wetlands populated by natrophilic (salt loving) plant communities. The wetlands are
designed to retain the extracted water for 10-20 minutes to allow adequate time for particulates
(i.e. oxidized iron and manganese) to settle out, and to trap or absorb other contaminants of
9 The Feasibility Study (URS, May 2010) indicated 10 groundwater extraction wells would be used to
contain/capture plume of groundwater contamination. The July feasibility study addendum revised the number of
wells to 12.
32
ecological concern. It is anticipated a portion of the CPEC load including ammonium/nitrogen,
metals and phosphorus will be taken up by, and sequestered within, the tissue of the natrophilic
plants.
After the pretreatment steps, the extracted water would be pumped to the northern end of the site
and land applied to approximately 8 acres of natrophilic grasses at agronomic rates using spray
irrigation methods. The natrophilic grasses were chosen for the land application area to target
and take-up CPECs such as barium, chloride, and calcium. The grass stand will be irrigated at a
rate of about 1.9 inches per month during the months of May through September depending on
actual weather and operating conditions. Soil moisture sensors, lysimeters, groundwater
monitoring wells, and soil quality will be monitored to assure water is applied at agronomic rates
and is not having a deleterious effect on the agricultural productivity of land and the beneficial
uses of the underlying groundwater.
Prior to constructing a full scale pretreatment system and planting the land application area, pilot
testing will be conducted to evaluate the effectiveness of various treatment trains and to identify
the appropriate configuration and sizing of treatment system components.
There may be periods when land application is not feasible and it is necessary to provide
temporary storage of the extracted water until crop irrigation can be resumed. The FS addendum
indicates a lined pond with 60,000 to 80,000 cubic feet of storage capacity (approximately one
month‟s flow based on an extraction rate of 15 gpm) is a component of the remedy.
The estimated total cost including capital, monitoring and operation and maintenance costs of the
remedy is estimated at $4.96 million.
4.5.3 Alternative 2b: Groundwater Extraction (Wells), Pretreatment , and Discharge to Tualatin River
Under alternative 2b pretreatment of the extracted groundwater is identical to that described in
alternative 2a, however, rather than applying the treated water to agricultural land it is directly
discharged via a conveyance pipe to the Tualatin River. This alternative presumes pretreatment
of the extracted groundwater reduces CPECs and TMDL related contaminants below remedial
action cleanup levels established at Lakeside and that these levels are met at the end of the
discharge pipe.
The total projected cost of this remedy alternative including capital, recurring and future costs is
$4.4 million.
4.5.4 Alternative 3: Groundwater Extraction Trench or Horizontal Extraction Wells, Pretreatment and Land Application or Direct Discharge
Alternative 3 is identical to alternative 2a, however, a 1300 feet trench would be installed for
pumping groundwater as an alternative to the 12 vertical wells. Pumping would hydraulically
control the plume of groundwater contamination preventing its discharge to the Tualatin River.
Extracted groundwater is treated above ground and land applied or directly discharged
(depending on the effectiveness of pretreatment) as described in alternatives 2a and 2b.
33
Rreversal of hydraulic gradients and groundwater capture and containment would occur within
hours to days after starting the pumps. The estimated total cost of the remedy presuming a 20
year operational period is $4.7-$5.2 million.
4.5.5 Alternative 4: Impermeable Barrier
Under Alternative 4, a subsurface barrier, such as sheet pile or slurry wall would be installed to
prevent groundwater discharge into the Tualatin. A 1300 feet barrier would be “keyed” into
underlying low permeability strata such as the Helevtia Formation at Lakeside. The barrier‟s
effect would be immediate after construction. The estimated total remedy cost over operating
period, including monitoring, decommissioning, closure and contingencies is $3.2 million.
4.5.6 Alternative 5: Impermeable Barrier with Groundwater Extraction, Pretreatment, and Land Application or Direct Discharge
Under Alternative 5, an impermeable barrier would be installed as described in alternative 4 but
would include a groundwater extraction system to prevent groundwater from flowing around the
barrier and into the river. Extracted water would be pretreated and land applied or directly
discharged to the Tualatin River as described in alternatives 2a and 2b. Containment and control
would prevent contaminated groundwater discharges to the river within hours to days after
starting the pumps. The estimated total cost of the remedy is $ 5.7 -6.3 million for the anticipated
operating period of 20 years.
4.5.7 Alternative 6: Permeable Reactive Barrier
Under Alternative 6, permeable barriers would be installed that allows groundwater passage
through the wall while removing and/or treating contaminants. The barrier would be to depths of
35 to 40 feet along the 1300 foot landfill width that would be filled with materials such as
chelators, sorbents, reactive agents, or microorganisms. Reducing contaminant loading to the
Tualatin would take an estimated 9 to12 months based on groundwater velocities. The total
remedy cost is $3.0 million for the estimated operating period.
4.5.8 Alternative 7: Phytoremediation by Deep-Rooted Coniferous or Deciduous Trees
Under Alternative 7, trees would be used to remove, degrade, contain, and/or sequester
contaminants in soils, sediments and groundwater. Special cultivation practices train roots to
extend through a relatively thick vadose zone to the interface of saturated and unsaturated soils.
To achieve a fully functional phytoremediation barrier with maximum mitigation potential would
take at least 4-6 years after planting the trees. The estimated total remedy cost is $3.0 million for
the anticipated operating period of 20 years.
4.6 PERIODIC REVIEW, MONITORING AND CONTINGENCIES
Predicting the long-term effectiveness of any of the remedial action alternatives is difficult,
because of the site‟s many uncertainties including:
34
Heterogeneity in the subsurface environment.
Potential changes in future land use and zoning.
Changes in community concerns regarding remedial actions.
Long-term performance of remediation systems.
Periodic monitoring and review of the remedy‟s performance and a contingency plan would be
implemented if the remedy does not achieve the remedial action objectives. The objective of
these steps will be to maintain the selected remedy‟s overall protectiveness. The contingency
plan will consider the remedial action objectives identified in this report‟s Section 4.1.2 and
establish a series of decision criteria and corresponding response actions for potential problems.
The remedial design/remedial action work plan and adaptive management plan will describe
details of the remedy implementation. Section 7.3 discusses the framework of this plan. The
remedial design/remedial action work plan and adaptive management plan process is similar to
DEQ‟s contingency plan process outlined here.
The contingency plan will include the following components: 1) establish performance criteria
based on achieving the remedial action objectives within specific time-frames; 2) if monitoring
data exceed trigger values in select monitoring wells, Lakeside initiates an expanded monitoring
program; 3) if the supplemental monitoring data fails the remedial action objectives, evaluate
additional remedial actions needed to ensure adequate protection of human health and the
environment.
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5. EVALUATION OF REMEDIAL ACTION ALTERNATIVES
5.1 EVALUATION CRITERIA
DEQ regulations (OAR 340-122-0090) define the criteria used to evaluate the remedial action
alternatives described in Section 6. Included is a two-step approach to evaluate and select a
remedial action.
Step One, evaluate the remedial action‟s protectiveness; if it is not protective, the alternative is
unacceptable and the step two evaluation is unnecessary. Step two, evaluate the “protective”
remedial alternatives and compare them against five balancing factors. The five balancing factors
are: 1) effectiveness in achieving protection, 2) long-term reliability, 3) implementability, 4)
implementation risk, and 5) reasonableness of cost.
For hot spots, the evaluation proceeds as follows: 1) Determine how well each alternative treats
the identified hot spot; 2) Select and implement the alternative that compares most favorably
against these balancing factors, and complies with the hot spot criteria; and. 3) Then conduct a
residual risk assessment for the selected alternative to document that it is protective of human
health and the environment.
5.2 PROTECTIVENESS
DEQ evaluates a particular remedial action‟s protectiveness by comparing actual or estimated
future COC concentrations to the acceptable risk levels described in section 4.1 of this document.
DEQ anticipates that the maximum concentration of a contaminant of concern will exceed the
acceptable risk level for the following pathways or beneficial uses:
Groundwater discharge to surface water and maintenance of aquatic habitat
DEQ will require hydraulic analysis of shallow groundwater and/or water quality monitoring to
evaluate this pathway and to establish if a given remedial alternative is protective.
OAR 340-122-090 states that protectiveness may be achieved by any of the following methods:
Treatment
Excavation and off-site disposal
Engineering controls
Institutional controls
Any other method of protection
A combination of the above
36
With the exception of hot spots, there is no preference for any one of the above methods for
achieving protectiveness. Where a hot spot has been identified, OAR 340-122-0090(4)
establishes a preference for treatment, to the extent that it is feasible, and includes a higher
threshold for evaluating the reasonableness of costs for treatment.
5.2.1 Landfill Cover Alternatives
5.2.1.1 Alternative 1 – No Action
Under alternative 1 there would be no enhancements of the existing landfill cover and thus no
improvement in cover performance is anticipated. Generation of leachate within the landfill and
releases of leachate to the environment would continue. This alternative would require long term
reliance on a hydraulic containment system to protect the Tualatin River and does not attempt to
further control or eliminate sources of groundwater contamination. DEQ does not consider it
protective in the long term or acceptable.
5.2.1.2 Alternative 2 – Replacement of Existing Cover with an Impermeable Cap
Impermeable caps are a demonstrated effective technology for preventing surface water and
precipitation from infiltrating landfill waste and generating leachate. This alternative is capable
of achieving RAO#1, is considered protective, and is retained for further consideration of its
feasibility.
5.2.1.3 Alternative 3 – Enhancement of the Existing ET Cover
In theory, a properly constructed and maintained ET cover will provide sufficient moisture
storage and evapotranspiration potential to reduce deep infiltration of precipitation rates to the
point it prevents or sufficiently minimizes groundwater contamination. Under this scenario,
enhancement of the existing cover provides adequate environmental protection. This alternative
is retained for further consideration.
5.2.2 Groundwater Alternatives10
5.2.2.1 Alternative 1 - No Action
Alternative 1, as the heading suggests, involves taking no action to minimize potential human or
environmental exposure. No action translates into no additional contaminant concentration
reductions, no additional contaminant plume controls, and no additional engineering or
institutional controls. In this scenario, the potential would still exist for future human or
ecological exposures to groundwater/surface water contaminant levels that exceed the acceptable
risk criteria. Considering these circumstances DEQ concluded Alternative 1 is not adequately
protective and did not evaluate this alternative any further.
10
Evaluation of Groundwater Alternatives in this section focuses exclusively on containing the groundwater plume
of contamination and does discuss treatment or reuse of the extracted water.
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5.2.2.2 Alternative 2a and 2b – Groundwater Extraction Using Vertical Wells
Alternative 2 would contain and control landfill-impacted groundwater, and significantly reduce
contaminated groundwater discharges to the Tualatin River. Groundwater pumping is a common
and potentially effective method for mitigating groundwater contamination. DEQ considers this
alternative protective and considered it for further analysis.
5.2.2.3 Alternative 3 – Groundwater Extraction Trench or Horizontal Extraction Wells
Alternative 3 would use an extraction trench or horizontal wells to capture and contain
contaminated groundwater and significantly reduce its discharge to the Tualatin River. This
approach is a variation on alternative 2. DEQ considers it protective and considered it for further
analysis.
5.2.2.4 Alternative 4 – Impermeable Barrier without Groundwater Pumping
Alternative 4 would use an impermeable barrier to block groundwater flow towards the river.
Lacking any pumping influences, groundwater would simply move under, over, or around the
barrier and continue discharging to the river. This alternative would not reduce contaminant
loading to the river. Consequently DEQ does not consider it protective and did not evaluate this
alternative further.
5.2.2.5 Alternative 5 – Impermeable Barrier with Groundwater Pumping
Alternative 5 would couple an impermeable barrier with groundwater extraction wells. This
combination of elements could produce a protective remedy. However, contamination located
downgradient of the wall would be difficult to extract. DEQ considers this alternative protective
and considered it for further analysis.
5.2.2.6 Alternative 6 – Permeable Reactive Barrier
Alternative 6 would use a permeable reactive barrier to remove and/or treat groundwater
contaminants of concern. This method allows groundwater to pass unimpeded and discharge to
the Tualatin River. The remedy‟s protectiveness is highly uncertain, however, considering the
groundwater contaminants involved and their geochemical properties. Chloride is one
contaminant that is generally not mitigated by reactive barriers. Unless Lakeside conducts further
testing to verify its effectiveness, DEQ presumes this technology is not protective and did not
retain it for further analysis.
5.2.2.7 Alternative 7 – Phytoremediation
Alternative 7 relies on hybrid poplar and pine trees to hydraulically control, capture and treat the
contaminant plume. There are many uncertainties regarding this technology‟s effectiveness.
DEQ‟s main concerns with the technology in general areas its limited ability to capture
contaminated groundwater at depth and its inability to effectively treat chloride contamination.
Furthermore, it would take a minimum of 4 to6 years after planting for : 1) the trees to mature
and remedy performance was optimized, and 2) before remedy effectiveness could be fully
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evaluated However, based on a DEQ site visit to Lakeside in September 2009, the most obvious
and significant obstacle to implementing this remedy is a lack of available space to plant a
phytoremediation barrier downgradient of the landfill. Based on these concerns and questions
DEQ concluded phytoremediation technology was infeasible for groundwater control/treatment
and thus did not retain this technology for further consideration.
5.3 BALANCING FACTORS
DEQ evaluated the three “protective” remedial action alternatives against the following
balancing factors defined in OAR 340-122-0090(3):
Effectiveness in Achieving Protection. DEQ‟s evaluation of this factor considered the
following components:
Magnitude of the residual risk from untreated waste or treatment residuals, without
considering risk reduction achieved through on-site management of exposure
pathways (e.g., engineering and institutional controls). The characteristics of the
residuals are considered to the degree that they remain hazardous, based on their
volume, toxicity, mobility, propensity to bio-accumulate, and propensity to degrade.
Adequacy of any engineering and institutional controls necessary to manage residual
risks.
The extent to which the remedial action restores or protects existing or reasonably
likely future beneficial uses of water.
Adequacy of treatment technologies in meeting treatment objectives.
The time until remedial action objectives are achieved.
Long-term Reliability. DEQ‟s evaluation of this factor considered the following
components:
The reliability of treatment technologies in meeting treatment objectives.
The reliability of engineering and institutional controls needed to manage residual
risks, considering the hazardous substances involved and their characteristics, the
long-term effectiveness and enforceability of the controls and their ability to
prevent migration and manage risk.
The nature and degree of uncertainties associated with any necessary long-term
management (e.g., operations, maintenance, monitoring).
39
Implementability. DEQ„s evaluation of this factor considered the following
components:
Practical, technical, legal difficulties and unknowns associated with constructing and
implementing the technologies, engineering controls, and/or institutional controls,
including the potential for scheduling delays.
The ability to monitor the effectiveness of the remedy.
Consistency with regulatory requirements, and requirements for coordinating with
other public agencies and obtaining necessary approvals and permits.
Availability of necessary services, materials, equipment, and specialists, including
the availability of adequate wastewater treatment and disposal services.
Implementation Risk. This factor considers the remedy‟s effectiveness, reliability,
implementability, construction timeline and potential risks to receptors including: the
neighboring community, workers involved in remedy construction, and the
environment;
Reasonableness of Cost. This factor assesses the reasonableness of each remedial
alternative‟s costs, including capital, operation and maintenance, and periodic review
costs, as well as the net present value of all costs. For identified hot spots, treatment
costs are compared to the benefits to human health and the environment to determine if
the cost is proportionate.
In general, DEQ prefers the least expensive remedial action unless a more expensive
corrective action‟s additional cost yields proportionately greater benefits in terms of one
or more of the other balancing factors. For sites with hot spots in groundwater, DEQ
evaluates the remedial action‟s costs and its environmental benefits to determine the
degree to which the two factors are proportionate. DEQ uses a higher threshold for
evaluating the reasonableness of costs for treatment of hot spots than for remediating
non-hot spots. DEQ also considers cost sensitivities and uncertainties.
Table 7 describes in detail how each alternative compares to the balancing factors including all
sub-criteria. The sections below summarize the major conclusions derived from this comparison
and provide additional discussion about site complexities and tradeoffs between alternatives.
5.3.1 Cover Alternatives
5.3.1.1 Impermeable Cap
With proper maintenance and contingency measures, an impermeable cap would likely provide
long-term reliability with respect to preventing excessive infiltration into the underlying landfill
waste. However, an impermeable cap would require greater maintenance to respond to issues of
soil settlement that can stress and tear synthetic membranes, sloughing of the cover soil that can
40
expose the geomembrane to sun and photolytic breakdown. Impermeable caps trap landfill gases
that otherwise would vent through a conventional soil cap or ET cover. To address the buildup of
landfill gases and their potential off-site transport, an active gas collection system would have to
be installed in conjunction with the impermeable cap. Landfill gas collection systems require
long-term monitoring and maintenance. Failure of the landfill gas extraction system could result
in migration of landfill gases from the facility and onto adjacent properties, potentially resulting
in explosion hazards.
Impermeable caps have been successfully constructed at numerous landfills and it is a
technology that can be implemented at Lakeside. Other than removal of the existing vegetation
and regrading of the site, no site-specific conditions preclude construction of an impermeable
cap.
The estimated 30 year net present value cost of construction and maintenance of an impermeable
cap is approximately $8.0 million.
5.3.1.2 Enhanced ET Cover
Once established and meeting performance criteria, an enhanced ET cover would likely provide
long term reliability in protecting groundwater quality. Maintenance requirements for an
established ET cover is anticipated to be low. A mature mixed forest would help maintain slope
stability and provide long term self-sustaining habitat consistent with the surrounding Tualatin
River National Wildlife Refuge. Recent soil gas data collected by Lakeside suggests that this
remedy likely would not require a landfill gas collection system and that low concentrations of
landfill gases at the surface would vent passively through the cover. This eliminates a significant
maintenance responsibility and greatly reduces the potential for off-site landfill gas migration.
The enhanced ET cap has greater aesthetic appeal and provides higher quality wildlife habitat
than the impermeable cap. An ET cover of mixed tree species, as is planned, for the cover is also
consistent with the goals of the Tualatin River National Wildlife Refuge, which adjoins the
Lakeside site. The remedy coupled with the adaptive management process will capture the
benefits of an ET cover, while addressing the uncertainties and improving on the performance of
the existing cover.
The estimated 30 year net present value of implementing an enhanced ET cover is $2.3 million.
5.3.2 Groundwater Alternatives
5.3.2.1 Alternative 2 - Groundwater Extraction Wells
DEQ considers conventional groundwater extraction systems highly effective. Although, wells
are subject to clogging, wells that foul with precipitates or clog with sediment usually can be
reconditioned, redeveloped or if necessary, replaced to maintain their effectiveness. As a
consequence, DEQ assumes they will be reliable in the long term. Groundwater extraction wells
are a widely used technology that can be easily implemented at the site. There are no known
41
implementation risks associated with extraction well systems. This remedy‟s cost is $4.511
million and DEQ considers it reasonable.
5.3.2.2 Alternative 3 – Groundwater Extraction Using a Trench or Horizontal Wells
DEQ considers the cut-off trench or horizontal well system‟s effectiveness and long-term
reliability similar to that of a vertical–well groundwater extraction system. Implementing this
type of system is less certain, though, because of its complex construction requirements.
Potential technical challenges relate to the trench depths and the horizontal well system‟s
installation and maintenance over an area spanning 1300 feet of riverbank terrain. This
alternative does not appear to have any significant technical advantages over vertical wells and it
would cost $5.2 million.
5.3.2.3 Alternative 5 – Impermeable Barrier with Groundwater Extraction
This alternative is similar to other groundwater extraction and containment technologies
evaluated in the feasibility study but includes an impermeable-barrier component. DEQ
concludes that Alternative 5 (combined impermeable barrier and extraction system) would not be
more effective or protective than a groundwater extraction system alone. Installing the barrier
adds $1.1-1.8 million to the remedy‟s cost with no discernable benefit compared to other
groundwater extraction alternatives.
5.3.3 Extracted Groundwater Treatment and Disposal or Reuse
5.3.3.1.1 Option a. Chemically-Physically Treat Extracted Groundwater and Discharge to
Tualatin River
Technologies for chemical-physical treatment of groundwater contaminants at Lakeside are
effective and capable of attaining discharge limits established under an NPDES permit, further
modified by TMDL allocations. Components of the treatment system would include
oxidation/precipitation reactors, filtration media, and an advanced form of treatment such as
reverse osmosis and/or ion exchange to treat highly soluble contaminants such as barium,
chloride, and calcium. These wastewater treatment technologies have been demonstrated to be
reliable in the long-term, however, they have high operation and maintenance costs.
Regarding implementability, materials, design and construction services are available to install a
wastewater treatment plant. Furthermore, its effectiveness is easily monitored. Obtaining
authorization to discharge treated water to the Tualatin River under an NPDES permit or with a
permit exemption is uncertain. Groundwater contamination primarily poses an ecological risk,
human health exposures are not considered significant, and the on-site storage, treatment and
conveyance of contaminated groundwater are assumed to have very low implementation risks.
11
This cost estimate is based on a network of 10 extraction wells as described in the feasibility study. The
feasibility study addendum revised the proposed system to have 12 extraction wells. The addition of two extraction
wells will nominally increase the estimated cost of this remedy alternative.
42
Implementation risks associated with the discharge of treated water to the Tualatin River are also
considered very low.
Although the capital, operation, and maintenance costs associated with construction of the
treatment plant and associated outfall were not presented in the FS report, DEQ assumes they are
high relative to other wastewater treatment/disposal options. Costs are highly sensitive to rates
and volumes of extracted groundwater and chloride treatment requirements.
5.5.1.1.2 Option b. Chemical-Physical-Phyto Treatment and Discharge to Tualatin River
Technologies for chemical-physical-phyto treatment of groundwater contaminants at Lakeside
are available and may be capable of attaining discharge limits established under an NPDES
permit, further modified by TMDL allocations. Treatment effectiveness must be further
evaluated through pilot testing. Under this alternative, extracted groundwater would initially be
aerated primarily to oxidize metal CPECs to less soluble forms. The aerated water would then
be routed through an emergent wetland to filter particulate (including oxidized metals), remove
phosphate, and other CPECs. The ability to reduce all CPEC to levels below the remedial action
cleanup levels is uncertain. Once adequate treatment is established, these wastewater treatment
technologies have been demonstrated to be reliable in the long-term.
Regarding implementability, materials, design and construction services are available to install a
wastewater treatment plant. Furthermore, its effectiveness is easily monitored. Groundwater
contamination primarily poses an ecological risk, human health exposures are not considered
significant, and the on-site storage, treatment and conveyance of contaminated groundwater are
assumed to have very low implementation risks. Implementation risks associated with the
discharge of treated water to the Tualatin River are also considered very low.
Costs have a low to moderate sensitivity to rates and volumes of extracted groundwater.
5.3.3.1.3 Option c. Chemically-Physically Treat Extracted Groundwater and Apply to
Agriculatural/Forest Land
Land application is an effective, proven technology for wastewater treatment or reuse. The
contaminants and their concentration in groundwater at Lakeside are generally effectively taken
up by agricultural crops and trees and/or are immobilized in underlying soil. There is uncertainty
regarding the amount of area required to reuse the volume of water produced by the hydraulic
containment system. Current estimates indicate 8 acres of land will be sufficient to
accommodate the daily groundwater extraction rate. However, Lakeside appears to have enough
crop and/or forestland to accommodate a large range of flow rates. DEQ considers this option
implementable from a technical standpoint.
Land use requirements have been identified as a possible implementation issue for this option.
The proposed application area is in close proximity to the contamination and necessary for
remediation, meeting the regulatory definition of “on site” under OAR 340-122-115(37) and is
therefore subject to ORS 465.315(3). ORS 465.315 provides that for on-site portions of an
approved remedial action no state or local permit, license or other authorization will be required
43
for, and no procedural requirements will apply, although substantive requirements are not
affected. The land identified for land application is zoned EFU by Washington County. The
proposed land application of water appears to be compatible with substantive requirements of
land use zoning in the area and therefore does not appear to present a substantial
implementability barrier. Application of water for purposes of irrigation is a farm use allowed
without restriction in an EFU zone. Further, land application of reclaimed water or industrial
process is also a permitted use, in conjunction with DEQ approval of the land application
pursuant to its water quality authorities and a determination in conjunction with that approval,
that the application rates and site management practices for the land application ensure continued
agricultural, horticultural or silvicultural production and do not reduce the productivity of the
tract. Land application contemplated by this option would be pursuant to a DEQ approval under
its water quality authorities, either in the form of a permit or a permit exemption under ORS
465.315(3) that includes applicable substantive water quality requirements, including any
required determinations. Lakeside would be required to coordinate with local government bodies
as to substantive requirements and pay fees of such bodies as stated in ORS 465.315(3).
Implementation risks are primarily associated with contamination of underlying groundwater as
a result of over-application or over-irrigation. At Lakeside, land application would be monitored
using a network of groundwater monitoring wells and/or lysimeters to assure underlying
groundwater was not impacted. Implementation risks would be further mitigated by locating the
land application area upgradient of the Lakeside hydraulic containment system, and by
maintaining buffers between the application area and private properties not associated with
Lakeside or Grabhorn Inc.
The costs of this option have not been directly presented in the Feasibility Study Report,
however, they are assumed to be low relative to other options and also have a low sensitivity to
rates and volumes of groundwater extraction.
5.3.3.1.4 Option d. Haul Extracted Groundwater to a Collector Sanitary Sewer
Hauling contaminated groundwater and discharging it to the nearest sanitary sewer collector is
considered an effective and implementable option for disposing of extracted groundwater.
Municipal waste water treatment plants are proven effective and reliable in treating the
groundwater contaminants observed at Lakeside. The primary implementation risk is associated
with increases truck traffic on Vandermost and Scholls Ferry Roads and increased energy usage
and greenhouse gas emissions. Although Lakeside did not present costs for this option, trucking
expenses and disposal fees are considered high relative to other options. Total costs for this
option are highly sensitive to the rates and volumes of extracted groundwater.
5.3.3.1.5 Option e. Pipe Extracted Groundwater Directly to a Collector Sanitary Sewer
Piping extracted groundwater directly to a sanitary sewer collection point is considered a highly
effective, reliable and implementable technology. Implementation risks associated with the
remedy include leakage from piping and contamination of shallow groundwater. Moreover, there
is significant likelihood of implementation delay due to uncertainties of land use permitting and
construction. Although costs for this option were not presented in the FS, they are assumed high
44
compared to other wastewater treatment/disposal options. Because the POTW would charge a
discharge fee, the operation cost is sensitive to groundwater extraction rates and volumes.
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6. COMPARATIVE ANALYSIS OF ALTERNATIVES
In this section, DEQ uses the remedy selection criteria identified in Section 5.3 to compare the
landfill cover and groundwater remedial action alternatives for addressing the under-performing
cover and achieving the remedial action objectives.
6.1 LANDFILL COVER
6.1.1 Protectiveness
Both an enhanced ET cover and an impermeable cap are considered capable of achieving
sufficiently low average annual infiltration rates to prevent excessive leachate generation and
restore groundwater quality to levels there are protective of its beneficial uses.
6.1.2 Effectiveness
Both alternatives are considered potentially effective in achieving RAO #1, although a properly
installed and maintained impermeable cap would outperform an enhanced ET cover in reducing
infiltration rates. Furthermore, the impermeable cap is able to prevent precipitation from
infiltrating into the waste during years of exceptionally high rainfall that would likely overwhelm
the storage and removal capacity of the ET cover. A correctly installed and maintained
impermeable cap has greater effectiveness in controlling and limiting infiltration than an ET
cover.
6.1.3 Long-Term Reliability
A properly constructed and maintained impermeable cap is a reliable method for
reducing/preventing precipitation from infiltrating landfill waste. However, impermeable caps
are more susceptible to physical damage such as puncturing, tearing, and failure caused by soil
settlement and slope failure, and their longevity is uncertain to some degree Furthermore,
impermeable caps prevent the passive venting of landfill gases. To prevent the buildup of gases
beneath the cover and reduce their lateral transport, an active landfill gas collection system is
typically operated in conjunction with an impermeable cap. Landfill gas collection systems
require maintenance and monitoring and failure of the system could result in off-site gas
migration and associated safety risks.
A healthy community of grasses, shrubs and trees present on an ET cover can provide an
effective landfill cover in perpetuity. In addition, the network of tree, shrub and herbaceous roots
present within an ET cover stabilize slopes reducing the potential for failure. ET covers also are
relatively insensitive to settlement of the cover surface compared to an impermeable cap. An ET
cover allows landfill gases to vent passively preventing the buildup of gas pressure that can force
46
lateral transport of methane off of the facility property. Therefore it is unlikely a gas collection
system would be required. The absence of an active landfill gas collection system greatly
reduces long-term maintenance and monitoring requirements and potential safety concerns
relative to the impermeable cap.
Potential concerns affecting the long-term reliability of the ET cover include but are not limited
to: disease and/or rodent damage affecting the health of tree stands, wildfire, and a maturing soil
structure that can become increasingly permeable over time. A mature, properly functioning ET
cover is less vulnerable to catastrophic failure and is structurally more resilient than a
impermeable cover. Furthermore, it does not require the installation and maintenance of a
landfill gas collection system. As a consequence, an ET cover is anticipated to have greater
long-term reliability than an impermeable geosynthetic cover.
6.1.4 Implementability
No conditions have been identified that would prevent implementation of either remedy at the
site. Both remedies are considered equally implementable.
6.1.5 Implementation Risk
A synthetic impermeable landfill cover at Lakeside will trap landfill gases, likely requiring
installation of a gas collection system to prevent their off-site migration. An active gas collection
system would have to be operated, monitored, and maintained to prevent the off-site migration of
methane at unsafe levels and pressures. An unanticipated shut down of the gas collection
system, or simply impaired system performance, could result in offsite migration of methane
towards inhabited structures.
No implementation risks are known to be associated with enhancement of the ET cover.
Considering potential implementation risks associated with the impermeable cap, the ET cover is
the preferred alternative.
6.1.6 Reasonableness of Cost
The cost of constructing and maintaining the enhanced ET cover is $2.3 million as compared to
$8.0 million for the impermeable cap. The ET Cover has a substantial cost advantage over the
impermeable cap.
6.1.6 Comparative Analysis Summary
Although the impermeable cap will likely out perform an enhanced ET cover both are considered
protective and capable of achieving design objectives. Both remedies are considered
implementable at the site. Implementation risk for installing an impermeable cap is higher,
although not easily quantified. The enhanced ET cover is substantially less expensive to
implement than an impermeable cap ($2.3 million compared to $8.0 million). Furthermore, the
enhanced ET cap has greater aesthetic appeal and provides higher quality wildlife habitat than
the impermeable cap. Based on consideration of these factors, DEQ recommends implementation
of the enhanced ET cap as the remedy to achieve RAO #1.
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6.2 GROUNDWATER REMEDIAL ACTION ALTERNATIVES
In this section, DEQ uses the remedy selection criteria identified in Section 5.3 to compare the
three remedial action alternatives.
6.2.1 Protectiveness
The four remedial action alternatives 2a, 2b, 3 and 5 each extract groundwater to establish
hydraulic control and prevent its discharge to the Tualatin River. DEQ recognizes there are
numerous well designs and network configurations that will achieve RAO #2 and thus have
equivalent protectiveness. Furthermore, an extraction well network can easily be augmented or
modified to decrease, enlarge or alter the shape of the groundwater containment area. Inclusion
of a barrier in the design provides only nominal enhancement of the protectiveness of the
groundwater extraction remedies.
Land application treatment is considered the most protective as contaminant load in the
wastewater would not be discharged to the river. Chemical treatment would likely not reduce
concentrations of certain chemicals such as chloride and it therefore considered less protective.
6.2.2 Effectiveness
As indicated previously, the four remedial action alternatives for groundwater extraction each
have equivalent effectiveness. The horizontal wells are more difficult to adjust the distribution of
extraction rates compared to vertical wells and thus have less flexibility to adjust to a non-
uniform groundwater flow field or non-uniform distribution of contamination. Inclusion of a
barrier in the groundwater capture and containment system nominally improves the effectiveness
of capture. While all proposed remedies are roughly equivalent in effectiveness, alternative 5
using vertical extraction wells with a wall is marginally better.
Chemical treatment has limitations for certain chemicals. Land application treatment has been
effective elsewhere for treatment of more-concentrated landfill leachate.
6.2.3 Long Term Reliability
Alternatives 2a, 2b, 3, and 5 have equivalent long-term reliability. Long-term operation has
some uncertainties and maintenance of horizontal wells is more difficult than in vertical wells.
Horizontal extraction well technology is less broadly used than vertical extraction wells and
general industry experience using them in remedial applications is much more limited. A
network of vertical wells would utilize individual pumps for each well. In contrast, a system
using horizontal wells would use fewer larger pumps to achieve the same level of capture. As a
consequence, during equipment breakdowns and routine maintenance, the horizontal extraction
wells are more vulnerable to a complete loss of hydraulic containment than a network of vertical
wells. Furthermore, the use of variable speed pumps in vertical wells allows for increases in
extraction rates to temporarily compensate for the loss of an adjacent extraction well. Based on
these factors, DEQ considers Alternatives 2a, 2b and 5 to be highly reliable and Alternative 3
only moderately reliable.
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Land application treatment has been demonstrated as reliable in similar applications and is
considered to be the most reliable treatment option. Chemical treatment has limitations for
certain chemicals.
6.2.4 Implementability
Alternative 3, which uses horizontal extraction wells, on balance is the most easily implemented
of the four remedies. Horizontal wells use directional drilling techniques that are capable of
installing multiple long linear wells from a single location. The directional drilling technique
allows horizontal wells to be installed in areas with limited or no access and without constructing
drilling pads. Fewer contractors install horizontal wells and the technique requires specialized
drilling equipment, but this is not thought to strongly impact the implementability of the remedy.
Alternatives 2a and 2b use conventional well drilling techniques to construct a network of
vertical extraction wells that collectively form a hydraulic barrier. Vertical wells are used in the
most common extraction systems and the materials, equipment, and contractors for installing
them are readily available. However, unlike the horizontal wells, the drilling rig must have
access to each location a vertical well is drilled. At Lakeside an existing road runs along the toe
of the landfill that roughly coincides or parallels the proposed extraction well alignment, thus
access issues are greatly reduced.
Alternative 5 requires deep trenching using specialized equipment, and is a much more difficult
construction technique than drilling vertical extraction wells or directional drilling for the
horizontal wells. The preferred alignment of the barrier present significant implementation
challenges. Between the access road and the river is most desired location based on the site
topography and proximity to the river. The installation of a barrier in this area would likely
require extensive removal of mature riparian area vegetation.
DEQ concluded installation of horizontal wells is the most implementable groundwater remedy,
closely followed by a system using vertical wells. Installation of a barrier with an extraction
system, alternative 5, is the least implementable remedy due to the effort required to install the
barrier.
Land application of wastewater would be relatively straightforward to implement as Grabhorn
currently grows Christmas trees on adjacent parcels of land.
6.2.5 Implementation Risk
DEQ‟s evaluation of implementation risks associated with the various hydraulic
control/groundwater extraction systems focused on potential environmental impacts resulting
from their installation. DEQ is unaware of any significant implementation risks associated with
remedial alternative 3. Remedial alternatives 2a and 2b require considerable greater disturbance
of the riparian area within which the wells would be located. Each well requires its own leveled,
cleared drilling pad, thus mature riparian vegetation would disturbed or lost as result of the well
drilling activities.
49
Installation of a barrier carries the greatest ecological implementation risk. This alternative
would likely result in the greatest disturbance (largest footprint) in the riparian area vegetation.
Furthermore, once RAO#1 has been met and an groundwater extraction system is no longer
required, the barrier would have to be removed to restore the natural groundwater discharges to
the reach of the Tualatin River. No removal or partial removal of the barrier wall could
permanently impact aquatic habitat within the Tualatin.
Trucking would pose the most implementation risk due to daily truck traffic to the wastewater
treatment plant. The primary implementation risk for land application is over-application
resulting in localized impacts to underlying shallow groundwater.
6.2.6 Reasonableness of Cost
Alternative 2 is the least costly alternative of the three carried forward in the analysis. At 4.4-4.9
million, it is $300,000 less than alternative 3 and $1.8 million less than alternative 5. Land
application treatment provides the best cost-benefit option as water is beneficially used.
6.2.7 Comparative Analysis Summary
Each of the remedial action alternatives is equivalent with respect to protectiveness and
effectiveness of achieving protection. Alternatives 2 and 5 have equivalent long-term reliability.
Alternative 2 is the most easily implemented remedy. The materials, equipment, and contractors
for installing vertical wells are readily available. Alternative 5 would require deep trenching
which is considerably more difficult to implement than installation of vertical extraction wells.
There are no significant implementation risks associated with these remedial alternatives.
Alternative 2 is the least costly alternative at $1.8 million less than Alternative 5. Based on the
comparative analysis, Alternative 2 best meets the balancing criteria for remedy selection. In
addition, land application treatment using trees is the best feasible and protective treatment
option for the extracted groundwater.
6.3 Treatment, Reuse and Disposal of Extracted Water
In this section, DEQ uses the remedy selection criteria identified in Section 5.3 to compare the
four alternatives for treating and reusing/disposing of extracted water.
6.3.1 Protectiveness
Options c, d and e
Land application treatment, option c, is considered more protective than options including direct
discharge (options a and b) since the contaminant load in the wastewater would not be
discharged directly to the river. Soils provide additional contaminant treatment and uptake
beyond pretreatment steps alone and moderates variation in the level of pre-treatment
effectiveness. Chemical-physical treatment alone would likely not achieve RACL for certain
chemicals such as chloride and it therefore is considered less protective.
50
Options d and e convey untreated extracted water to a publicly owned treatment works. Issues
concerning discharge of partially treated water, or land application impacting shallow
groundwater are eliminated and thus they provide the highest level of protectiveness.
6.3.2 Effectiveness
Trucking untreated water or conveying it through a pipeline and disposing of it at a public
treatment works is not considered effective as it is not a sustainable solution.
Option a, chemical-physical treatment of the extracted water, has limited effectiveness for certain
CPECs such as chloride and is unlikely to meet surface water discharge limits necessary for a
direct discharge to the Tualatin River..
The effectiveness and protectiveness of chemical-physical-phyto treatment of extracted
groundwater, as described in Option b, is somewhat uncertain and will need to be further
evaluated through pilot testing. It is assumed to be more effective than Option a, but may not
adequate to achieve discharge limits listed in an NPDES permit.
Option c, pretreatment with land application treatment has been effective elsewhere for treatment
of more-concentrated landfill leachate. While the pretreatment step is identical to Option b, the
additional step of land applying the pretreated water to natrophilic plants would be a polishing
step to provide more complete treatment of the extracted water. This method in theory provides
very effective wastewater treatment, greater than option a and option b, and less than options d
and e.
6.3.3 Long Term Reliability
Once the groundwater pretreatment system is installed, tuned, and optimized, options a and b are
considered reliable alternatives. Changes in extracted water chemistry over time may require
adjustment of the treatment steps, but system operation is considered flexible enough to adapt to
changing conditions.
Option Land application Land application treatment has been demonstrated as reliable in similar
applications and is considered to be the most reliable treatment option. Loading rates to soils
with salts and other contaminants carry some uncertainty regarding useful life of an application
area, however, this should be clarified during the pilot testing phase. If the loading capacity of
the soil is exceeded before completion of the project this can be remedied by designating and
irrigating a backup application site.
Conveyance of untreated water to a public owned treatment works, Options d and e, are
equivalently the most reliable wastewater treatment options discussed in the feasibility study.
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6.3.4 Implementation Risk
Trucking would pose the most implementation risk due to daily truck traffic to the wastewater
treatment plant and high emissions of hazardous air pollutants and greenhouse gases. The
primary implementation risk for land application is over-application resulting in localized
impacts to underlying shallow groundwater.
6.3.5 Reasonableness of Cost
Alternative 2 is the least costly alternative of the three carried forward in the analysis. At 4.9
million, it is $300,000 less than alternative 3 and $1.8 million less than alternative 5. Land
application treatment provides the best cost-benefit option as water is beneficially used.
6.3.6 Comparative Analysis Summary
Each of the remedial action alternatives are equivalent with respect to protectiveness and
effectiveness of achieving protection. Alternatives 2 and 5 have equivalent long-term reliability.
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7. RECOMMENDED REMEDIAL ACTION ALTERNATIVES
Based on the evaluation of alternatives presented in Sections 6, DEQ has selected Landfill Cover
Alternative 3 - Enhanced ET Cover, and Groundwater Alternative 2 – Groundwater Extraction
with Wells and Land Application as the proposed remedial action at the Lakeside Reclamation
Landfill site. These alternatives would meet the the remedial action objectives and therefore
considered protective, best meet the balancing factors for remedy selection and treat hot spots of
contamination. A detailed description of the proposed actions is provided in following sections.
7.1 DESCRIPTION OF RECOMMENDED LANFILL COVER ALTERNATIVE
Alternative 3 would include extensive testing and surveys to evaluate soil conditions and identify
causes of stunted tree growth and high mortality rates. The results of this work would be used to
design additional testing and evaluation to enhancements to the cover to optimize its
performance. This may include but is not limited to: planting of more suitable tree species,
adding additional soil to provide sufficient moisture storage, reducing landfill gas levels in the
cover to enable deep rooting of trees, irrigating trees at critical times until they are self-sufficient.
To evaluate success in enhancing the cover, tree types, ages, health, growth rates and degree of
canopy closure will be tracked over time. To evaluate the effectiveness of the ET cover
instruments such as lysimeters and other tools will be used to monitor infiltration rates directly to
assure it achieves the performance criteria of less than 1.0 inch of deep infiltration annually, or
other infiltration rate demonstrated to be protective of groundwater quality.
7.2 DESCRIPTION OF THE RECOMMENDED GROUNDWATER ALTERNATIVE
7.2.1 Groundwater Extraction
The proposed groundwater remedy would involve installing vertical extraction wells between the
southern boundary of the waste disposal area and the Tualatin River. The extraction wells would
extract contaminated groundwater to capture and contain the portion of the groundwater plume
exceeding risk based concentrations for protection of Tualatin River. At this time it is presumed
the area of hydraulic containment is approximately 1500 feet long, extending to a depth of 40
feet below ground surface.
Preliminary groundwater modeling indicates 12 vertical wells would be necessary to effect
complete capture of the plume of groundwater contamination. The wells will be spaced
approximately120 to150 ft apart. The number of wells and their spacing may be adjusted after
taking into consideration the results of a recent aquifer test and refinement of the site
groundwater model. The extraction wells may be pulsed pumped and/or shut down on a seasonal
basis to reduce the volume of water extracted annually. The timing, pumping rates, and length of
pumping periods will be determined based on assuring contaminant plume capture, considering a
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variety of factors including groundwater seepage rates and the period and magnitude of gradient
reversals (relative to the Tualatin River).
Treatment of extracted groundwater will be accomplished by initially aerating the water to
oxidze dissolved metals then routing it through an emergent wetland for additional CPEC
removal and uptake. Pretreated water will be conveyed to a 60,000 to80,000 cubic feet storage
pond that is sized to provide approximately one-month storage at a groundwater extraction rate
of 15 gallon per min. Water will be withdrawn as needed to irrigate trees/crops at agronomic
rates using a spray irrigation system. Lakeside has estimated that approximately eight acres of
crop land growing natrophilic grasses will be required to accommodate the volumes of extracted
groundwater. In the July 2011 addendum to the feasibility study, Lakeside estimated that
approximately eight acres of crop land planted with natrophilic grasses are necessary to
accommodate the volumes of extracted water. The RDRA/AMP will provide a more detailed
assessment of the required acreage.
7.2.2 Protective Levels and Background Concentrations
Protective levels for shallow groundwater are specified in Table 6. Site contaminants of concern
are naturally occurring inorganic substances that may have natural background concentrations at
levels that exceed protective levels. In those cases, natural background levels are defined as
protective. Lakeside may request DEQ concurrence on natural background as protective levels
for those constituents based on a statistically valid evaluation of background shallow
groundwater quality. Subject to DEQ approval, these background concentrations would replace
the protective levels specified for the facility.
7.2.3 Development of a Final Design
Based on the number of sampling points, the location and dimensions of the groundwater plume
requiring remedial action can only be approximated. As part of remedial design, the targeted
groundwater capture zone must be defined. An investigation will be performed to more
accurately delineate the vertical and horizontal extent of contamination exceeding remedial
action limits. This investigation will likely involve depth discrete sampling of groundwater, and
will also provide the bases for locating additional compliance wells.
7.2.4 Performance Monitoring
Evaluation of remedy effectiveness will be based on: 1) groundwater elevation and river stage
data for a hydraulic analysis of groundwater containment, and 2) water quality monitoring at
wells located between the extraction wells and the Tualatin River. The primary line of evidence
for demonstrating the remedy is successful is the reduction of groundwater contaminant levels to
below remedial action limits in the performance monitoring well network. A secondary, and
likely the initial, line of evidence for remedy success is groundwater elevation and river stage
data that demonstrate hydraulic containment of the contaminant plume is achieved and
maintained. DEQ anticipates additional groundwater wells will be installed to fully and
effectively monitor remedy performance and evaluate compliance with remedial action levels.
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7.3 Adaptive Management
The proposed remedy may be modified through time through a process of adaptive management.
Adaptive management is a structured approach very similar to the DEQ contingency
development process triggered when certain remedy elements prove deficient in achieving
remedial objectives. The structured AMP process focuses on dealing with uncertainty in the
decision making for resource management. It is well-suited to ecological systems and problems
with uncertainty or complexity. In the context of the groundwater remedy implementation at
Lakeside, the generalized elements of adaptive management are as follows:
1. Assess problem and develop conceptual model of the system (e.g., ET cover must minimize
infiltration as characterized by a water-balance model).
2. Establish mitigation goals (e.g., Feasibility Study Remedial Action Objectiveness).
3. Identify and implement management actions or remedial actions (e.g., FS alternatives, such
as cover planting scheme and groundwater treatment methods).
4. Identify performance criteria (can be stated in terms of a hypothesis in the adaptive
management process). Clearly state hypotheses to assess performance criteria.
5. Design and implement a monitoring plan to collect data to test hypotheses.
6. Compare monitoring results to performance criteria by testing hypotheses with monitoring
data.
7. Continue management actions, or revise management actions, or adjust performance criteria
based on monitoring results and analysis. For example:
7a. If goals met, then remedial action or mitigation is complete (“no further action
determination by the DEQ).
7b. If goals not met, but criteria and actions are supported, continue management action
and AM process (i.e., continue remedial action).
7c. If goals not met, and data do not support hypothesis, criteria, or actions, revise
management actions (i.e., take contingent actions) and/or change the performance
criteria through the adaptive management process.
Elements of adaptive management are well-suited to projects such as the Lakeside Landfill
closure and mitigation project, where uncertainties favor a flexible and iterative approach over a
prescriptive plan. A landfill ET cover system is a complex combination of physical, chemical,
and biological conditions, such as native and imported soils, a variety of native and non-native
vegetation, variable landfill gas concentrations, and varying soil bulk densities. In such
environments, the uncertainties make it complex to predict the outcome of closure management
actions, especially where little baseline information is available, such as for ET covers in western
Oregon. Adaptive management is the process by which ecological conditions are monitored and
enhanced to trend conditions toward the stated goals and performance benchmarks, or “success
criteria”.
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Although the process is structured, the adaptive management method promotes flexible decision
making that reflects improved understanding of the site conditions and outcomes of management
actions. Monitoring of outcomes advances scientific understanding and helps adjust actions and
criteria as part of an iterative learning process. It is not a “trial and error” process, rather it
emphasizes learning by doing. Adaptive management is not an end in itself but a means to make
more effective decisions with enhanced benefits.
Flexibility is an important component of adaptive management, so the potential responses cover
a broad range of possibilities. In adaptive management, the desired range of remedial outcomes
or habitat characteristics is met by applying site-specific environmental information in an
iterative framework of measurement and response. Within this framework, success or failure are
not evaluated by any one single goal. Instead, if one or more goals are not being met,
management strategies (or other adjustments) are adapted to reflect the monitoring data.
Responses to monitoring data may include continued operation and maintenance of specified
management actions (e.g., continue specified operation and monitoring of groundwater pumping
and treatment systems), additional monitoring, literature research, experiments, consultations
with discipline experts, re-evaluation, changes to current management strategies, and/or
reassessment of goals and success criteria.
Remedy implementation and adaptive management at Lakeside will be described further in a
Remedial Design/Remedial Action and Adaptive Management Plan. It is recommended that
implementation of the RDRA/AMP (subject to agency review and approval) be incorporated into
the Record of Decision.
7.4 RESIDUAL RISK ASSESSMENT
OAR 340-122-084(4)(c) requires a residual risk evaluation of the recommended alternative that
demonstrates that the standards specified in OAR 340-122-0040 will be met, namely:
Assure protection of present and future public health, safety, and welfare, and the
environment
Achieve acceptable risk levels
For designated hot spots of contamination, evaluate whether treatment is reasonably
likely to restore or protect a beneficial use within a reasonable time
Prevent or minimize future releases and migration of hazardous substances in the
environment
No formal residual risk assessment was presented in the Feasibility Study. Based on the
assumption of complete capture of groundwater exceeding applicable ecologically risk-based
criteria, no residual risks are anticipated.
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8. ADMINISTRATIVE RECORD INDEX
The Administrative Record consists of the documents on which the recommended remedial
action for the site is based. The primary documents used in evaluating remedial action
alternatives for the Lakeside Reclamation Landfill site are listed below. Additional background
and supporting information can be found in the Lakeside Reclamation Landfill project file
located at DEQ Northwest Region Office, 2020 SW 4th
Avenue, Suite 400, Portland, Oregon.
SITE-SPECIFIC DOCUMENTS
Voluntary Agreement for Remedial Investigation/Feasibility Study between Grabhorn Inc. and
ODEQ (DEQ NO. LQVC-NWR-05-08), December 9, 2005
Parametrix. Reconnaissance Boring and Monitoring Well Installation. December 2006
URS. Level I Scoping Ecological Risk Assessment, Lakeside Reclamation Landfill. March 2007
URS. Work Plan for Remedial Investigation – Lakeside Landfill, May 2007
URS. Beneficial Water Use and Land Use Determination – Lakeside Reclamation Landfill,
September 2007
URS. Benthic Macroinvertebrate Bioassessment Study – Lakeside Reclamation Landfill.
November 2007
URS. Supplemental Remedial Investigation Work Plan – Lakeside Reclamation Landfill.
October 2008
Parametrix. 2008 Annual Environmental Monitoring Report – Lakeside Reclamation Landfill.
February 2009
Parametrix. 2009 Annual Environmental Monitoring Report – Lakeside Reclamation Landfill.
February 2010
Parametrix. 2010 Annual Environmental Monitoring Report – Lakeside Reclamation Landfill.
February 2011
URS. Tualatin River Sediment Sampling - Lakeside Reclamation Landfill, URS June 2009
URS. Response to DEQ June 6, 2008 Comments on the Level II Screening Ecological Risk
Assessment – Lakeside Reclamation Landfill Remedial Investigation. June 2009
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URS. Technical Memorandum. Revised FS Work Plan for the Lakeside Landfill: Outline of Plan
for Groundwater Modeling. July 2009
URS. Technical Memorandum. Revised FS Work Plan for the Lakeside Landfill: Outline of Plan
for Analysis of Closure Cover. July 2009
URS. Screening-Level Human Health Risk Assessment & Level II Screening Ecological Risk
Assessment, URS, July 2009
URS. Work Plan for Feasibility Study – Lakeside Reclamation Landfill. August 2009
URS. Remedial Investigation Report – Lakeside Landfill. September 2009
URS. Feasibility Study – Lakeside Reclamation Landfill. May 2010
URS. Addendum to Feasibility Study, Land Application Treatment of Extracted Groundwater –
Lakeside Reclamation Landfill. July 2011
STATE OF OREGON
Oregon‟s Environmental Cleanup Laws, Oregon Revised Statutes 465.200-.900, as amended by
the Oregon Legislature in 1995.
Oregon‟s Hazardous Substance Remedial Action Rules, Oregon Administrative Rules, Chapter
340, Division 122, adopted by the Environmental Quality Commission in 1997.
Oregon‟s Hazardous Waste Rules, Chapter 340, Divisions 100 - 120.
Oregon‟s Water Quality Criteria, Chapter 340, Division 41, [RIVER] Basin.
Oregon‟s Groundwater Protection Act, Oregon Revised Statutes, Chapter 468B.
United States Geological Survey
USGS, Sources and Transport of Phosphorus and Nitrogen During Low-Flow Conditions in the
Tualatin River, Oregon, 1991-93. Water-Supply Paper 2465-C
Other
Metcalf And Eddy, Wastewater Engineering, Treatment, Disposal and Reuse, Third Edition.
McGraw-Hill, 1991.
GUIDANCE AND TECHNICAL INFORMATION
DEQ. Cleanup Program Quality Assurance Policy. September 1990, updated April 2001.
DEQ. Consideration of Land Use in Environmental Remedial Actions. July 1998.
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DEQ. Guidance for Conducting Beneficial Water Use Determinations at Environmental Cleanup
Sites. July 1998.
DEQ. Guidance for Conduct of Deterministic Human Health Risk Assessment. May 1998
(updated 5/00).
DEQ. Guidance for Conducting Feasibility Studies. July 1998.
DEQ. Guidance for Ecological Risk Assessment: Levels I, II, III, IV. April 1998 (updated
12/01).
DEQ. Guidance for Identification of Hot Spots. April 1998.
DEQ. Guidance for Use of Institutional Controls. April 1998.
USEPA. Guidance for Conducting Remedial Investigation and Feasibility Studies Under
CERCLA. Office of Emergency and Remedial Response. OSWER Directive 9355.3-01. October
1988.
USEPA. Transport and Rate of Contaminants in the Subsurface. Robert S. Kerr Environmental
Research Laboratory. EPA/625/489/019. 1989.
USEPA. Exposure Factors Handbook. Office of Health and Environmental Assessment.
EPA/600/8-89/043. May 1989.
USEPA. Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation
Manual, Part A, Interim Final. Office of Solid Waste and Emergency Response. EPA/540/1-
89/002. December 1989
USEPA. Human Health Evaluation Manual, Supplemental Guidance: Standard Default Exposure
Factors. OSWER Directive No. 9285.6-03, March 1991.
USEPA. Effectiveness of groundwater pumping as a restoration technology. U.S. Environmental
Protection Agency ORNL/TM-11866. May1991.
USEPA. Supplemental guidance for Superfund Risk Assessments in Region 10. U.S.
Environmental Protection Agency. August 1991.
USEPA. Integrated Risk Information System. Office of Research and Development. Cincinnati,
Ohio. 1992.
USEPA. Pump-And Treat Ground-Water Remediation, A Guide For Decision Makers And
Practitioners. U.S. Environmental Protection Agency. EPA/625/R-95/005. July 1996.
Verschueren, Karel. Handbook of Environmental Data on Organic Chemicals. Van Nostrand
Reinhold, New York. 1983.
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